FA311系列高速并條機(jī)車頭箱的設(shè)計(jì)【說明書+CAD+SOLIDWORKS】,說明書+CAD+SOLIDWORKS,FA311系列高速并條機(jī)車頭箱的設(shè)計(jì)【說明書+CAD+SOLIDWORKS】,fa311,系列,高速,并條,機(jī)車頭,設(shè)計(jì),說明書,仿單,cad,solidworks 揚(yáng) 州 市 職 業(yè) 大 學(xué) 畢 業(yè) 設(shè) 計(jì) 設(shè)計(jì)題目：FA311系列高速并條機(jī) 車頭箱的設(shè)計(jì) 系 別：機(jī)械工程系 專 業(yè)：機(jī)械制造工藝及設(shè)備 班 級(jí)：01機(jī)械（2）班 姓 名： 學(xué) 號(hào)： 指導(dǎo)老師： 完成時(shí)間： 目錄 一、 畢業(yè)設(shè)計(jì)的目的——————————?。? 二、 課題簡介　————————————?。? 三、箱體結(jié)構(gòu)的設(shè)計(jì)———————————　４ 四、結(jié)構(gòu)尺寸的設(shè)計(jì)計(jì)算—————————　５ 五、軸的設(shè)計(jì)——————————————　１９ 六、參考文獻(xiàn)——————————————?。玻? 七、畢業(yè)小結(jié)——————————————?。玻? 一、畢業(yè)設(shè)計(jì)的目的 畢業(yè)設(shè)計(jì)是學(xué)生完成本專業(yè)的最后一個(gè)極為重要的實(shí)踐性教學(xué)環(huán)節(jié)，是使學(xué)生綜合運(yùn)用所學(xué)過的基本理論.基本知識(shí)與基本技能去解決專業(yè)范圍內(nèi)的工程技術(shù)問題而進(jìn)行的一次基本訓(xùn)練，這對(duì)學(xué)生即將從事的有關(guān)技術(shù)工作和未來的開拓具有一定意義，其主要目的是： 1、學(xué)生綜合分析和解決本專業(yè)的一般工程技術(shù)問題的獨(dú)立工作能力，拓寬和深化學(xué)生的知識(shí)。 2、學(xué)生樹立正確的設(shè)計(jì)思路，設(shè)計(jì)構(gòu)思和創(chuàng)新思維，掌握工程設(shè)計(jì)的一般程序.規(guī)范和方法。 3、學(xué)生正確使用技術(shù)資料.國家標(biāo)準(zhǔn)，有關(guān)手冊(cè).圖冊(cè)等工具書。進(jìn)行設(shè)計(jì)計(jì)算.數(shù)據(jù)處理.編寫技術(shù)文件等方面的工作能力。 4、 學(xué)生今昔功能調(diào)查研究。面向?qū)嶋H。面向生產(chǎn)。向工人和工程技術(shù)人員學(xué)習(xí)的基本工作態(tài)度.工作作風(fēng)和工作方法。 二、課題簡介 FA311系列高速并條機(jī)適應(yīng)于75mm以下的纖維的純紡與混紡，在紡紗工藝過程中，位于梳棉工序之后，梳棉纖維條經(jīng)過本機(jī)并合與牽伸，能夠提高纖維的條長片段均勻度、纖維的伸直度，使不同品質(zhì)纖維的混合更趨均勻，為獲得良好的細(xì)紗創(chuàng)造必要的條件。 2100型號(hào)的車頭箱是陜西寶雞寶成紡織機(jī)械長的產(chǎn)品，年產(chǎn)量1000臺(tái)，車頭箱是FA311系列高速并條機(jī)的主要?jiǎng)恿鬟f機(jī)構(gòu)，它通過按一定的速比排布的齒輪將電機(jī)的動(dòng)力經(jīng)車頭箱的變速，傳遞給各工作主軸，使其獲得一定的動(dòng)力、轉(zhuǎn)速和方向。 該車頭箱是鑄造而成，內(nèi)部的零件主要由圓柱斜齒輪組成，齒輪要求加工精度較高，生產(chǎn)批量大。針對(duì)生產(chǎn)現(xiàn)狀和要求設(shè)計(jì)2100型號(hào)的車頭箱。 由被加工零件的不同，并條機(jī)設(shè)計(jì)方案各異，其車頭箱可以垂直或水平安裝。該設(shè)計(jì)的車頭箱是水平安裝在FA311高速并條機(jī)右側(cè)上方的。 三、 確定箱體結(jié)構(gòu)、繪制原始依據(jù)圖 車頭箱箱體及前后蓋，均采用灰鑄鐵HT200鑄造而成，箱體的形狀和尺寸按國家標(biāo)準(zhǔn)GB3668-83和實(shí)際設(shè)計(jì)情況選擇。 箱體長度 L=L1=L2+L3+L4 式中：L1是左端臺(tái)座的長度 L2是齒輪縱向軸系方向上兩最遠(yuǎn)齒輪的中心距 L3是兩端厚度之和 L4是兩最遠(yuǎn)軸距箱體壁的長度 則L=195+30+530+182=937 箱體寬度B=B1+B2+B3+B4 式中:B1是橫向最大軸系齒輪寬度 B2是箱體厚度 B3軸端至箱壁的距離 B4突出箱蓋的寬度 則B=125+30+40+56=251 箱體的高度H=H1+H2+H3 式中H1是軸系高度方向上兩最遠(yuǎn)主軸的中心距 H2是兩最遠(yuǎn)主軸的中心距箱壁的距離 H3是箱體的厚度 則H=354+180+45=569 最后結(jié)合設(shè)計(jì)手冊(cè)與實(shí)際的結(jié)構(gòu)尺寸確定箱體的尺寸為 L×B×H=940×254×573 四、結(jié)構(gòu)尺寸設(shè)計(jì) 已知：電機(jī)功率P=1.8KW,電機(jī)轉(zhuǎn)速n=1470r/min nⅰ1=1006r/min, nⅱ5=n電機(jī)=1470r/min, nⅲ7=2123r/min, nⅳ15=205r/min, nⅴ17=143r/min 1) 確定傳動(dòng)比及分配傳動(dòng)比 總傳動(dòng)比： iⅰ總=n電機(jī)/n1=1470/1006=1.5 iⅱ總=n電機(jī)/n5=1470/1470=1 i?？?n電機(jī)/n7=1470/2123=0.7 iⅳ總=n電機(jī)/n15=1470/205=7.2 iⅴ總=n電機(jī)/n17=1470/143=10.3 傳動(dòng)比的分配： iⅰ總=i45×i23×i12 則：i45 =1.46 i23=1.77 i12=0.565 iⅱ總=i5=1 iⅲ總=i56×i67 則：i56=1.10 i67=0.63 iⅳ總=i45×i48×i9 10×i11 12×i13 14×i14 15 則：i45=1.46 i48=1.18 i9 10=1.14 i11 12=3 i13 14=1.34 i14 15=0.92 iⅴ總=i45×i48×i9 10×i11 12×i13 16×i16 17 則：i13 16=1.34 i16 17=1.31 2)、運(yùn)動(dòng)參數(shù)的和動(dòng)力參數(shù)的設(shè)計(jì) （1）各輸出軸速度已知： nⅰ1=1006r/min nⅱ5=n電機(jī)=1470r/min nⅲ7=2123r/min nⅳ15=205r/min nⅴ17=143r/min 則其它各軸的轉(zhuǎn)速為： nⅰ34=n電機(jī)/i45=1470/1.46=1006r/min nⅰ2= nⅰ34/i23=1006/1.77=586 r/min nⅰ=1006 r/min nⅱ5=n電機(jī)=1470r/min nⅲ6= nⅱ5/i56=1470/1.10=11336 r/min nⅲ7= nⅲ6/i67=1336/0.63=2123 r/min nⅳ34=1006 r/min nⅳ89= nⅳ34/i48=1006/1.18=853 r/min nⅳ10 11= nⅳ89/i9 10=853/1.14=748 r/min nⅳ12 13= nⅳ10 11/i11 12=748/3=249 r/min nⅳ14= nⅳ12 13/i14=249/1.34=186 r/min nⅳ15= 205 r/min nⅴ16= nⅳ12 13/i13 16=249/1.34=186 r/min nⅴ17= 143 r/min （2）各軸的功率： 電機(jī)到各傳動(dòng)軸的效率： ηⅠ1=η1·η2·η3=0.96×0.98×0.97=0.82 ηⅠ2=η1·η22·η32 =0.96×0.982×0.972=0.87 ηⅠ34=η1·η23·η33=0.96×0.983=0.91 ηⅡ5=η1·η2=0.96×0.98=0.94 ηⅢ6=η1·η2·η3=0.96×0.98×0.97=0.91 ηⅢ7=η1·η22·η32=0.96×0.982×0.972=0.87 ηⅣ89=η1·η22·η32=0.96×0.982×0.972=0.87 ηⅣ10 11=η1·η23·η33=0.96×0.983×0.973=0.82 ηⅣ12 13=η1·η24·η34=0.96×0.984×0.974=0.78 ηⅣ14=η1·η25·η35=0.96×0.985×0.975=0.75 ηⅣ15=η1·η26·η36=0.96×0.986×0.976=0.71 ηⅴ16=η1·η25·η35=0.96×0.985×0.975=0.75 ηⅴ17=η1·η26·η36=0.96×0.986×0.976=0.71 查《機(jī)械設(shè)計(jì)實(shí)訓(xùn)教程》 ∮1=0.96（V帶傳動(dòng)效率） ∮2=0.98（滾動(dòng)軸承的傳動(dòng)效率） ∮3=0.97（齒輪精度為8級(jí)） 實(shí)際功率： P電機(jī)=1.8KW Pⅰ1= P電機(jī)·ηⅠ1=1.8×0.82=1.18 KW Pⅰ2= P電機(jī)·ηⅠ2=1.8×0.87=1.57 KW Pⅰ34= P電機(jī)·ηⅠ34=1.8×0.91=1.64 KW Pⅱ5= P電機(jī)·ηⅡ5=1.8×0.94=1.70 KW Pⅲ6= P電機(jī)·ηⅢ6=1.8×0.91=1.64 KW Pⅲ7 P電機(jī)·ηⅢ7=1.8×0.87=1.57 KW Pⅳ89= P電機(jī)·ηⅣ89=1.8×0.87=1.57 KW Pⅳ10 11= P電機(jī)·ηⅣ10 11=1.8×0.82=1.48 KW Pⅳ12 13= P電機(jī)·ηⅣ12 13=1.8×0.78=1.4 KW Pⅳ14= P電機(jī)·ηⅣ14=1.8×0.75=1.35 KW Pⅳ15= P電機(jī)·ηⅣ15=1.8×0.71=1.26 KW Pⅴ16= P電機(jī)·ηⅴ16=1.8×0.75=1.35 KW Pⅴ17= P電機(jī)·ηⅴ16=1.8×0.71=1.26 KW （3）各軸的扭矩： 電機(jī)軸：T0=9550P/n=9550×1.8/1470=11.69 N·M Tⅰ1=9550 Pⅰ1/nⅰ1=9550×1.48/1006=14.05 N·M Tⅰ2=9550 Pⅰ1/nⅰ2=9550×1.57/568=26.4 N·M Tⅰ34=9550 Pⅰ1/nⅰ34=9550×1.64/1006=15.6 N·M Tⅱ5 =9550 Pⅱ5/nⅱ5=9550×1.7/1470=11.04 N·M Tⅲ6=9550 Pⅲ6=9550×1.64/1336=11.7 N·M Tⅲ7=9550 Pⅲ7=9550×1.57/2123=7.06 N·M Tⅳ89=9550 Pⅳ89=9550×1.57/853=17.6 N·M Tⅳ10 11=9550 Pⅳ10 11=9550×1.48/748=18.9 N·M Tⅳ12 13=9550 Pⅳ12 13=9550×1.4/249=53.7 N·M Tⅳ14=9550 Pⅳ14=9550×1.35/186=69.3 N·M Tⅳ15=9550 Pⅳ15=9550×1.26/205=58.7 N·M Tⅴ16=9550Pⅴ16=9550×1.35/186=69.3 N·M Tⅴ17=9550Pⅴ17=9550×1.26/143=84.1 N·M 3、選擇齒輪材料并確定許用應(yīng)力 1)查《機(jī)械設(shè)計(jì)基礎(chǔ)》表6-9大小齒輪均采用45鋼調(diào)質(zhì)，齒面硬度分別為240BHS ,200HBS. 由圖6-30 ，6-31查得σHlim5=580MPa σFlim5=460MPa σHlim4=540 MPa σFlim4=420 MPa 取SHmin=1 SFmin=1 〔σH5〕=σHlim1/SHmin=580/1=580 MPa 〔σH5〕=σHlim2/SHmin=540/1=540 MPa 〔σF4〕=σFlim1/ SFmin=460/1=460 MPa 〔σF4〕=σFlim2/ SFmin=420/1=420 MPa 2) 按齒面接觸疲勞強(qiáng)度設(shè)計(jì)計(jì)算 d≧3√(590/σH) 2·KT1(i+1)/￠di 傳遞扭矩: T5=9.55×106 ·P電機(jī)/n=9.55×106×1.8/1470=11694 N·M 載荷系數(shù)K:因?yàn)橛休p微的沖擊，齒輪相對(duì)軸承對(duì)稱，由《機(jī)械設(shè)計(jì)基礎(chǔ)》表6-6取K=1.0,齒寬系數(shù)￠d：由《機(jī)械設(shè)計(jì)基礎(chǔ)》表6-7取 ￠d=0.4 許用接觸應(yīng)力〔σH〕：〔σH〕=〔σH2〕=540MPa 傳動(dòng)比：i=1.46 將以上參數(shù)代入上式，得 d≧3√(590/σH) 2·KT1(i+1)/￠di =3√（590/540）2×11694×（1.46+1）/0.4×1.46=30mm 取接觸應(yīng)力直徑為：d5=52mm 3)確定齒輪的參數(shù)及主要尺寸 齒數(shù)： 初選參數(shù)：輸入軸齒數(shù)Z5=39 Z4=i·Z5=1.46×39=57 模數(shù)： 初選螺旋角 β=20° 則法面模數(shù): mn=d5 cosβ/ Z5=52×cos20°/39=1.25 取標(biāo)準(zhǔn)植 mn=2 標(biāo)準(zhǔn)中心距： a45= mn (Z5 +Z4)/2 cosβ=2×(39+57)/2×cos20°100.9 mm 為了便于箱體加工和測(cè)量 取a=100 mm 則實(shí)際螺旋角 βˊ= arc cos mn(Z5 +Z4)/2a= arc cos2×(39+57)/2×100=16.26° 在8°～25°范圍內(nèi)合適 4）其它主要尺寸的計(jì)算: 分度圓直徑: d5= mn·Z5/ cosβˊ=2×39/cos16.26°=81.25 mm d4 =mn·Z4/ cosβˊ=2×57/cos16.26°=118.75 mm 齒頂圓直徑： da5= d5+2 mn=81.25+2×2=85.25 mm da4= d4+2 mn=118.75+2×2=122.75 mm 齒根圓直徑： df5= d5-2 mn((ha﹡+c﹡)=81.25-2×2(1+0.25)=76.25 mm df4= d4-2 mn((ha﹡+c﹡)=118.75-2×2(1+0.25)=113.75 mm 齒寬： b=￠d·d5=0.4×81.25=32.5 mm 則取齒寬b=32 mm 5）驗(yàn)算齒根彎曲疲勞強(qiáng)度： σF=1.6KT1 cosβ/b mn d1 ·Yfs≦〔σF〕 當(dāng)量齒數(shù)Zv: Zv5=z5/cos3βˊ=39/ cos316.26°=44.08 Zv4=z4/cos3βˊ=57/ cos316.26°=64.432 復(fù)合齒形系數(shù)：Yfs 根據(jù)Zv5 ，Zv4查《機(jī)械設(shè)計(jì)基礎(chǔ)》得 Yfs5=3.85 Yfs4=4.0 σF5=1.6KT1 cosβ/b mn d1 ·Yfs5 =1.6×1×11694×cos20°×3.85/32×2×81.25=13 Mpa ﹤〔σF〕 σF4=σF5·Yfs4/Yfs5=13×4.0/3.85=13.5 Mpa ﹤〔σF〕 彎曲疲勞強(qiáng)度足夠 6）確定齒輪傳動(dòng)精度： 齒輪圓周速度 V=πd5n5/60×1000 =3.14×81.25×1470/60×1000=6.25 m/s 查《機(jī)械設(shè)計(jì)基礎(chǔ)》表6-4確定公差組均為8級(jí)精度。 7）計(jì)算齒合力 圓周力 Ft=2T1/d5=2×11694/81.25=287.85 N 徑向力 Fr= Ft tan an/ cosβˊ=287.85×tan20°/cos16.26°=109 N 軸向力 Fa=Ft Ft tan an=287.85×tan20°=104.77 N 4、其它齒輪的設(shè)計(jì)計(jì)算 1) i12 =0.565 i23=1.77 m=2 β=20° βˊ=16.26° 初選齒數(shù) Z3=39 Z2= Z3· i23=39×1.77=69 Z1= Z2· i12=69×0.565=39 中心距 a23= mn (Z3 +Z2)/2 cosβ=2×(39+69)/2×cos20°=113.6 mm a12= mn (Z2 +Z1)/2 cosβ=2×(69+39)/2×cos20°=113.6 mm 取標(biāo)準(zhǔn)中心距a23=115 mm a12=115 mm 分度圓的直徑： d3= mn·Z3/ cosβˊ=2×39/cos16.26°=81.25 mm d2= mn·Z2/ cosβˊ=2×69/cos16.26°=143.75 mm d1= mn·Z1/ cosβˊ=2×39/cos16.26°=81.25 mm 齒頂圓直徑： da3= d3+2 mn=81.25+2×2=85.25 mm da2= d2+2 mn=143.75+2×2=147.75 mm da1= d1+2 mn=81.25+2×2=85.25 mm 齒根圓直徑： df3= d3-2 mn((ha﹡+c﹡)=81.25-2×2(1+0.25)=76.25 mm df2= d2-2 mn((ha﹡+c﹡)=143.75-2×2(1+0.25)=138.75 mm df1= d1-2 mn((ha﹡+c﹡)=81.25-2×2(1+0.25)=76.25 mm 2) Z5=39 i56=1.1 i67=0.63 m=2 β=20° βˊ=16.26° 則 Z6= i56·Z5=1.1×39=43 Z7= i67·Z6=0.63×43=27 中心距： a56= mn (Z5 +Z6)/2 cosβ=2×(39+43)/2×cos20°=87.26 mm a67= mn (Z6 +Z7)/2 cosβ=2×(43+27)/2×cos20°=74.49 mm 取標(biāo)準(zhǔn)中心距 a56=88 mm a67=75 mm 分度圓直徑： d6= mn·Z6/ cosβˊ=2×43/cos16.26°=89.58 mm d7= mn·Z7/ cosβˊ=2×27/cos16.26°=56.25 mm 齒頂圓直徑： da6= d6+2 mn=89.58+2×2=93.58 mm da7= d7+2 mn=56.25+2×2=60.25 mm 齒根圓直徑： df6= d6-2 mn((ha﹡+c﹡)=89.58-2×2(1+0.25)=84.58 mm df7= d72 mn((ha﹡+c﹡)=56.25-2×2(1+0.25)=51.25 mm 3) Z4=57 i48=1.18 m=2 β=20° βˊ=16.26° Z8= i48 ·Z4=1.18×57=67 中心距： a48= mn (Z4+Z8)/2 cosβ=2×(57+67)/2×cos20°=131.95 mm 取標(biāo)準(zhǔn)中心距 a48=132 mm 分度圓直徑： d8= mn·Z8/ cosβˊ=2×67/cos16.26°=139.58 mm 齒頂圓直徑： da8= d8+2 mn=139.58+2×2=143.58 mm 齒根圓直徑： df8= d8-2 mn((ha﹡+c﹡)=139.58-2×2(1+0.25)=134.58 mm 4) i9 10=1.14 i11 12=3 m=2 β=20° βˊ=16.26° 初選參數(shù)： Z9=52 Z11=33 則 Z10= i9 10·Z9=1.14×52=59 Z12= i11 12·Z11=3×33=99 中心距： a9 10= mn (Z9+Z10)/2 cosβ=2×(52+59)/2×cos20°=118.12 mm a11 12= mn (Z11+Z12)/2 cosβ=2×(33+99)/2×cos20°=140.47 mm 取標(biāo)準(zhǔn)中心距 a9 10=120 mm a11 12=140 mm 分度圓直徑： d9= mn·Z9/ cosβˊ=2×52/cos16.26°=108.33 mm d10= mn·Z10/ cosβˊ=2×59/cos16.26°=122.92mm d11= mn·Z11/ cosβˊ=2×33/cos16.26°=68.75mm d12= mn·Z12/ cosβˊ=2×99/cos16.26°=2016.25mm 齒頂圓直徑： da9= d9+2 mn=108.33+2×2=112.33 mm da10= d10+2 mn=122.52+2×2=126.92 mm da11= d11+2 mn=68.75+2×2=72.75 mm da12= d12+2 mn=206.5+2×2=210.25 mm 齒根圓直徑： df9= d9-2 mn((ha﹡+c﹡)=108.33-2×2(1+0.25)=103.33 mm df10= d10-2 mn((ha﹡+c﹡)=122.92-2×2(1+0.25)=117.92 mm df11= d11-2 mn((ha﹡+c﹡)=68.75-2×2(1+0.25)=63.75 mm df12= d12-2 mn((ha﹡+c﹡)=206.25-2×2(1+0.25)=201.25 mm 5) i13 14=1.34 i14 15=0.92 i13 16=1.34 i16 17=1.31 m=2 β=20° βˊ=16.26° 初選參數(shù)： Z13=44 則 Z14= i13 14·Z13=1.34×44=59 Z15= i14 15·Z14=0.92×59=54 Z16= i13 16·Z13=1.34×44=59 Z17= i16 17·Z16=1.31×59=77 中心距： A13 14= mn (Z13+Z14)/2 cosβ=2×(44+59)/2×cos20°=109.61 mm a14 15= mn (Z14+Z15)/2 cosβ=2×(59+54)/2×cos20°=120.25mm a13 16= mn (Z13+Z16)/2 cosβ=2×(44+59)/2×cos20°=109.61mm a16 17= mn (Z16+Z17)/2 cosβ=2×(59+77/2×cos20°=144.73mm 取標(biāo)準(zhǔn)中心距 a13 14=110 mm a14 15=120 mm a13 16=110 mm a16 17=145 mm 分度圓直徑： d13= mn·Z13/ cosβˊ=2×44/cos16.26°=91.67 mm d14= mn·Z14/ cosβˊ=2×59/cos16.26°=122.92 mm d15= mn·Z15/ cosβˊ=2×54/cos16.26°=112.5 mm d16= mn·Z16/ cosβˊ=2×59/cos16.26°=122.92 mm d17= mn·Z17/ cosβˊ=2×77/cos16.26°=160.42 mm 齒頂圓直徑： da13= d13+2 mn=91.67+2×2=95.67 mm da14= d14+2 mn=122.52+2×2=126.92 mm da15= d15+2 mn=112.5+2×2=116.5 mm da16= d16+2 mn=122.92+2×2=126.92 mm da17= d17+2 mn=160.42+2×2=164.42 mm 齒根圓直徑： df13= d13-2 mn((ha﹡+c﹡)=91.67-2×2(1+0.25)=86.67 mm df14= d14-2 mn((ha﹡+c﹡)=122.92-2×2(1+0.25)=117.92 mm df15= d15-2 mn((ha﹡+c﹡)=112.5-2×2(1+0.25)=107.5 mm df16= d16-2 mn((ha﹡+c﹡)=122.92-2×2(1+0.25)=117.92 mm df17= d17-2 mn((ha﹡+c﹡)=160.42-2×2(1+0.25)=155.42 mm 五、軸的設(shè)計(jì) 1、 選軸的材料和熱處理方法 車頭箱減速器是一般用途的減速器，所以軸的材料選用45鋼經(jīng)調(diào)治處理，便能滿足使用要求。45鋼經(jīng)調(diào)治處理后硬度為217~255HBS。 由<<機(jī)械設(shè)計(jì)手冊(cè)>>查得： бB=650Mpa бs=360 Mpa б-1=300 Mpa [б-1]=60 Mpa 2、 按扭矩強(qiáng)度估算軸的直徑 軸的最小直徑計(jì)算公式為： dmin≥A 3√p/n 由<<機(jī)械設(shè)計(jì)基礎(chǔ)>>查得： A=118~107 則 dmin5≥A 3√p/n =（118~107）×3√1.7/1470=12.4~11.3 mm 在Z5軸上，估取安裝軸承處的軸徑d0=35 mm ，安裝皮帶輪處的 軸徑d0=30 mm , 安裝齒輪處的軸徑d=40 mm ，安裝聯(lián)軸器軸端軸 徑為d0=30 mm ，軸上的其余軸徑尺寸由結(jié)構(gòu)要求而定。 3、 聯(lián)軸器的選擇 減速器輸出軸與壓輥軸采用彈性柱銷聯(lián)軸器，又前面計(jì)算知：T5=11.04N·M 由<<機(jī)械設(shè)計(jì)手冊(cè)>>查得：選用彈性柱銷聯(lián)軸器的型號(hào)為：TL5聯(lián)軸器， 30×82GB 4323B-84-1985 主要參數(shù)尺寸如下： 許用最大扭矩：125 N·m 許用最大轉(zhuǎn)速：3600r/min 主動(dòng)端d1=30mm J1型軸孔，L=82mm，A型鍵槽 從動(dòng)端d2=30mm J1型軸孔，L=82mm，A型鍵槽 4、 軸承的選擇 Z5軸為輸入，輸出，傳動(dòng)軸，既作用著徑向力Fr，又作用著軸向力，故選用深溝球軸承，型號(hào)為107 GB276-86 其主要尺寸如下：d=35mm D=62mm B=20mm 5、 軸的結(jié)構(gòu)設(shè)計(jì) 在Z5軸上兩端的軸承以選用107 GB276-85型號(hào)，與軸承配合的軸徑為35mm, 以軸肩作為軸向定位，因此在安裝齒輪處的軸徑不小于35mm，齒輪的齒根圓直徑只有76mm，故齒輪應(yīng)采用齒輪軸結(jié)構(gòu)。 6、 軸的強(qiáng)度計(jì)算 以Z5軸為例，根據(jù)Z5軸的結(jié)構(gòu)設(shè)計(jì)和箱體尺寸要求取L=500mm，L/2=250mm，由前面計(jì)算知： T5=11.04NM Ft5=287.5N Fr5=109N Fa5=104.77N 1) 根據(jù)軸系部件結(jié)構(gòu)作出軸系空間力圖 (a) 2) 作出Z5軸垂直平面受力圖，求支反力RAV、RBV，畫彎矩圖MV , 如圖 (b) RBV=(5/2·Fa5+L/2· Fr5)/500=(81.25/2×104.7+500/2×109)/500=63.N RAV= RBV- Fr5=62-109= -46 N 齒輪中心面左側(cè)彎矩MV1 MV1= RAV·L/2=46×(500/2) =11500 N·m 齒輪中心面右側(cè)彎矩圖MV2 MV2= RBV·L/2=32×(500/2) =15500 N·m 3)作出Z5軸平面受力圖，求支反力RAH RBH , 如圖 （C） 畫彎矩圖MH RAH= RBH= Ft5/2=287.5/2=143.75 N MH= RAH(L/2)=143.72×(500/2)=35937.5 N·mm 支反力RA RB，繪總彎矩圖M RA=√RAV2 + RBH2=√462 +143.752=150.9 N RB= √RBV2 + RAH2=√632 +143.752=156.9 N 齒輪中心面左側(cè)總彎矩圖M1 M1=√MV 12 + MV22=√115002 +35937.52=37693.6 N·mm 齒輪中心面右側(cè)總彎矩圖M2 M2=√MV22 + MH2=√15500 2+35937.52=39107 N·mm 5）繪轉(zhuǎn)矩圖 （d） 6)繪制當(dāng)量彎矩圖 Mc 如圖 （f） 因?yàn)槠л? 單向傳動(dòng)，從安全角度出發(fā)，軸上的轉(zhuǎn)矩T5按脈沖當(dāng)量循環(huán)考慮，故取校正系數(shù)a=0.6 齒輪中心面處最大當(dāng)量彎矩Mc為： Mc1=√M12 +（aT5）2=√37693.62 +(0.611×11040) 2=146441.3 N·mm Mc2=√M22+（aT5）2 =√397107 2+(0.611×11040) 2=157267.7 N·mm 取Mc= Mc2=157267.7 N·mm 7）選危險(xiǎn)截面進(jìn)行強(qiáng)度核算 根據(jù)當(dāng)量彎矩圖，初選中心面為危險(xiǎn)截面，該截面有鍵槽，故應(yīng)將軸徑加大5% 由此得： d≥1.05×3√Mc/0.1×[б-1] =1.05×3√157267.7/0.1×60=31.19 mm 由計(jì)算結(jié)果可知，軸徑小于安裝齒輪處的實(shí)際軸徑，所以強(qiáng)度足夠 7、 軸承的壽命計(jì)算 以Z5軸為例，Z5軸軸承以選用型號(hào)為30211的一對(duì)圓珠滾子軸承正裝。 其有關(guān)數(shù)據(jù)如下： C=86.5KN e=0.4 Y=1.5 載荷系數(shù). fp=1.1 溫度系數(shù)ft=1.0 軸承受力情況如下： 由前面計(jì)算知：RA=150.9 N RB=156.9 N RA RB 即為軸承徑向力FrA FrB FrA = RA=150.9 N FrB =RB=156.9 N 1) 計(jì)算內(nèi)部軸向力S SA= FrA/2Y=150.9/2×1.5=50.3 N SB= FrB/2Y=156.9/2×1.5=52.3 N 2) 計(jì)算實(shí)際軸向力 FaA=〔SA, SB-Fa5〕=max〔50.3, 52.3-104.7〕=50.3 N FaB=〔SA, SB+ Fa5〕=min〔50.3, 52.3+104.7〕=155 N 3）計(jì)算當(dāng)量動(dòng)載荷 P PA=fp(XA FrA+YA FaA)=1.1×(1×150.9+0×50.3)=165.99 N PB= fp(XB FrB+YB FaB)=1.1×(154.9+0×155) =170.39 N 8、 計(jì)算軸承的額定壽命Lh 因?yàn)镻A> PB，所以按右側(cè)軸承計(jì)算軸承的額定壽命Lh Lh=106 (ftC/PB) 3/60n=106×(1×86500/170.39)/60×1470=57557.6 h 9、選用鍵并校核強(qiáng)度 以Z5軸為例，Z5軸　上安裝齒輪處選用鍵的型號(hào)為A型鍵， １６×５２GB/T1979, b=16mm h=8mm L=56mm 鍵槽深t=4mm 鍵的工作長度為L=56-４＝５２mm T5=11.04N·M d=40mm 因?yàn)閷?duì)于按標(biāo)準(zhǔn)選擇的平鍵連接具有足夠的減切強(qiáng)度，故按擠壓強(qiáng)度計(jì)算 校核 ρp=4T/dhl=4×11040/40×8×52=26.5 Mpa 由《機(jī)械設(shè)計(jì)基礎(chǔ)》查得鍵連接的許用擠壓壓力[б] p=125～１５０Mpa 顯然ρp<[б] p　，故連接強(qiáng)度足夠，能夠滿足要求，安全。 參考文獻(xiàn) [1]郭愛蓮：《新編機(jī)械工程技術(shù)手冊(cè)》，經(jīng)濟(jì)日?qǐng)?bào)出版社1991年； [2]李恒權(quán)、朱明臣、王德云：《畢業(yè)設(shè)計(jì)指導(dǎo)書》，青島海洋大學(xué)出版社1993年第1版； [3]孟憲源：《現(xiàn)代機(jī)構(gòu)手冊(cè)》（下冊(cè)），機(jī)械工業(yè)出版社，1994年6月； [4]黃繼昌、徐巧魚、張海貴、范天保、季炳文：《實(shí)用機(jī)械構(gòu)圖冊(cè)》，人民郵電出版社，1996年6月； [5]徐錦康：《機(jī)械設(shè)計(jì)》，高等教育出版社； [6]徐玲花、游文明：《工程材料及熱加工》，揚(yáng)州市職業(yè)大學(xué)，1999年4月； [7]《模數(shù)設(shè)計(jì)基礎(chǔ)》機(jī)械工業(yè)出版社，1994年6月　　　　　　　　　　　　　　　　　 [8]《機(jī)械零件》 高等教育出版社 鄭志祥 周全光 主編 [9]《機(jī)械傳動(dòng)設(shè)計(jì)手冊(cè)》 煤炭工業(yè)出版社 江耕華 陳起松 主編 [10] 《機(jī)械設(shè)計(jì)基礎(chǔ)》 高等教育出版社 隋明洋 主編 畢業(yè)設(shè)計(jì)小結(jié) 兩個(gè)月時(shí)間的畢業(yè)設(shè)計(jì)遇期而終心情輕松之中略帶幾份收獲的喜悅，覺得總結(jié)一下很有必要，經(jīng)過這一段時(shí)間的畢業(yè)設(shè)計(jì)，深刻體會(huì)到設(shè)計(jì)的艱難，時(shí)間雖短，但非常高興的學(xué)到平時(shí)課堂上所不能學(xué)到的東西——實(shí)踐與理論的互助的認(rèn)識(shí)。 　我們初臺(tái)設(shè)計(jì)時(shí)候，因遇到從來沒有用過的軟件功能，導(dǎo)致對(duì)設(shè)計(jì)無從著手地步。最后得到教師的指點(diǎn)，才正確地進(jìn)入設(shè)計(jì)程序中，我們深智能設(shè)計(jì)不易，仍專細(xì)致的做?；叵肫鸬谝淮萎媹D，翻了多少書，問了多少人，經(jīng)過多次計(jì)算，修改，才將一個(gè)略為準(zhǔn)確的圖畫出來，一步步走向完善，其他零件也足如此，多次觀察、計(jì)算、修改。才繪制出零件的準(zhǔn)確性，得到較完善的零件。經(jīng)過兩個(gè)月的時(shí)間繪制如減速器的七十幾個(gè)零件，經(jīng)過多次組裝，多次修改，完成了它的裝配，設(shè)計(jì)過程中經(jīng)常會(huì)出現(xiàn)這樣那樣的結(jié)構(gòu)錯(cuò)誤都被指導(dǎo)老師及時(shí)指正過來，在職段設(shè)計(jì)過程中，收獲不少對(duì)設(shè)計(jì)又有了進(jìn)一步的認(rèn)識(shí)。 不過相信，不斷積累這些體會(huì)性的經(jīng)驗(yàn)，我們的設(shè)計(jì)思路，原理原則，認(rèn)識(shí)見識(shí)會(huì)日趨完善的。 最后，感謝指導(dǎo)教師老師的幫助！ 27 第22頁 遼寧科技大學(xué)本科生畢業(yè)設(shè)計(jì) Method of operating a mixer type hot metal car for the transport of molten iron and a device for carrying out the method Abstract A hot metal car is used for the transport of molten pig iron from a blast furnace to a steel making plant, the car having an opening through which it is filled and emptied. To restrict heat loss from the car, the opening is closed during at least one of (a) the journey from the blast furnace station to the steel making plant and (b) the journey from the steel making plant back to the blast furnace by a disposable cover which is at least partly lost into the molten iron during the course of the emptying or filling of the car at the end of the journey concerned. Inventors: Baas, Willem (Heemskerk, NL) Hof, Tette (Heemskerk, NL) Comes, Heinrich (Borken, DE) Jaunich, Helmut (Raesfeld, DE) Krampe, Hubert (Reken, DE) BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a method of operating a mixer type hot metal car for the transport of molten iron, particularly in conveying pig iron from a blast furnace to a steel making plant, and to a device for carrying out this method. 2. Description of the Prior Art In the steel industry, pig iron manufactured in a blast furnace is usually conveyed in the liquid state to a steel making plant by means of transport vessel known as a mixer type hot metal car. Another name used for this vehicle is a torpedo car. This hot metal car is a rail vehicle having a torpedo-shaped transfer vessel which is lined on its inside with refractory bricks and is supported on a bogie at each end. The transfer vessel is provided with an opening, known as the pouring mouth, which during filling with pig iron and while the transfer vessel is being conveyed is located at the top of the transfer vessel. The transfer vessel is rotated about its longitudinal axis to empty the vessel, so that the pig iron is discharged through the opening into a receiver. An example of such a car is given in Netherlands patent application No. 68.14343 (U.S. Pat. No. 3,661,374). In practice, the transfer vessel is filled at a blast furnace with molten pig iron at about 1500° C., and is then conveyed to a steel making plant. The pig iron is transferred from the vessel into a receiver in the steel making plant and the empty vessel is returned to a blast furnace to be refilled with pig iron. Sometimes an intermediate stop is made on the outward journey with the full vessel, during which the pig iron in the vessel subjected to treatment, typically being desulphurised. For this purpose a lance is inserted into the vessel through the opening. In a steel works a number of such cars are simultaneously in operation. The cycle time of a car is an average of 15 hours, comprising 3 hours for filling, 6 hours for the outward journey and 6 hours for return of the empty vessel. In practice these average times regularly show considerable variations because stops are made for various reasons during the outward and return journey. An example of a stop made on the return journey is when a car is temporarily put out of operation. One problem with the known method is that heat loss occurs whilst the car is in operation. Some of this heat loss is the result of radiation and convection from the outside surface of the vessel; more heat loss is due mainly to heat radiation through the opening from the inside of the vessel to the atmosphere. Heat loss during the outward journey means that the pig iron is supplied to the steel making plant at a lower temperature than that at which it is filled into the vessel. If there is and extremely long stop, this may mean that the pig iron can no longer be processed in the steel making plant. Because of heat loss during the return journey, the refractory brick in the empty vessel cools down. This also leads to a lower temperature of the pig iron when supplied to the steel making plant, since the pig iron, when charged into the vessel at the blast furnace, loses heat to the brick. Also, if the brick cools down considerably as a result of a long return journey, cracks may then occur in the brick thereby reducing the life of the brick. SUMMARY OF THE INVENTION The object of the invention is to provide a method of operating a mixer type hot metal car for molten iron in which the heat loss through the opening of the transfer vessel is reduced. A further object of the invention is to provide low cost, simple and safe device for reducing the heat loss through the opening of the transfer vessel for molten iron. According to the invention, a disposable cover is fitted to seal the opening of the vessel, after it is filled and/or after discharge of the iron from the vessel in order to reduce the heat loss from the vessel through the opening, and the cover is allowed to be carried away with the iron at the end of the subsequent journey when the pig iron is discharged from the vessel or the vessel is filled with a further charge respectively, so that the cover is at least partly lost into the iron. Preferably a disposable cover is employed in this manner in each of the journey from the filling location to the discharge station and the journey from the discharge station to the next filling station. One advantage of the method according to the invention is that greater use of scrap is possible in the steel making plant as a result of the higher temperature at which the pig iron is supplied to the plant, thereby providing a crude steel cost price advantage. Another advantage arises when the method is employed during the return of an empty transfer vessel. Due to the improved heat retention of the refractory brick in the transfer vessel savings can be achieved in the costs of additional heating of the brick because the number of occasions when the brick temperature is too low is reduced. Moreover, a longer brick life is achieved by greater heat retention because no cracks are formed. Moreover, cheaper types of refractory material may be used for the brickwork in the vessel. Because a disposable cover is used in the method according to the invention, the above advantages may be obtained with only one extra operating step, namely fitting a cover at the beginning of the outward and/or return journey. The method according to the invention is also safe because the cover need not be removed at the end of the journey. If the pig iron is desulphurised in the transfer vessel, the lance used for this should preferably be inserted into the vessel through a hole in the cover in the region of the opening in the vessel. This hole is preferably made in the cover by perforating the cover by means of the lance when introducing it into the vessel. Preferably also, before such a treatment of the pig iron, at least one further hole is made in the cover in the region of the opening in the vessel to allow the gases formed during the treatment to escape. A further advantage of the method, during desulphurisation, is that the mixer can be filled to a greater degree than if no cover is used. Without the use of a cover, the degree of filling is limited because of the danger of splashing during desulphurisation. Because of the higher permitted degree of filling the transfer vessel costs per tonne of pig iron can be reduced. When a cover is used on the empty transfer vessel according to the invention, the hole in the cover for subsequently filling the transfer vessel with pig iron is preferably made by pouring the pig iron onto the cover when starting to fill the vessel. A device for carrying out the method of the invention comprises a disposable cover for closing the opening of the vessel and means for retaining the cover on the vessel. The retaining means should be effective to hold the cover in place under all anticipated conditions, such as wind strength. The cover should meet requirements for resistance to the radiation from the inside of the transfer vessel and for the desired insulation value. The retaining means are all the more essential if the cover is light because of its disposable character. In one preferred embodiment the retaining means consist of part of the cover which extends into the opening, at least over a certain distance, and is located close to the edge of the opening. The part projecting into the opening should preferably be a wall structure which is closed circumferentially. In order to protect the refractory lining at the opening during filling of the vessel, at least temporarily. The part extending into the opening has preferably a tapered outer surface, so that when placed on the vessel the cover tends to wedge in the opening and this tapering part is preferably resiliently deformable so that it is adapted to the shape of the opening when fitted. ve-mentioned circumferentially closed wall structure. For desulphurisation purposes the cover is preferably provided with at least one prefabricated weak point in the region of the opening, which can be mechanically perforated e.g. by pushing with a pointed body. In an embodiment wich is preferred under certain conditions, the cover has a collar extending outside the area of the opening. This collar at least partially protects the refractory lining on the outside of the opening when the transfer vessel is being filled with pig iron. In selection of the material of the disposable cover, consideration must be given to the desideratum that the cover should not give rise to any undesirable additives in the pig iron and/or slag when it is lost into the vessel on filling or into the receiver on discharge. In one preferred embodiment of the cover, in which a hole can be made for filling the vessel with pig iron, the cover, at least locally in the area of the vessel opening, is made so that it collapses (loses structural integrity) under the influence of liquid pig iron, forming a hole. To this end, the cover preferably has a cup-shaped part or depression extending into the opening, the bottom of which collapses into the hole formed when the liquid pig iron is poured into the depression. The hole is formed by the impulse of the pig iron jet, which falls into the vessel during tapping of a blast furnace via a pig iron runner, and/or by the influence of the high temperature of the pig iron on the material from which the cover is made. The cover is preferably shaped so that vertical side wall of the cup consists of at least part of the height of the abo A preferred cover is manufactured at least partly from a material comprising at least 50% refractory filler material, 5-40% refractory fibrous material and 2-10% binding agent. It is worth mentioning that a mat of refractory fibres and binder has been proposed for use in contact with the surface of a molten metal bath to reduce heat loss, see e.g. U.S. Pat. No. 3,876,420, but there has apparently been no suggestion of the use of a disposable cover for the filling opening of a transport vessel. A hot metal car should be located carefully under the end of a pig iron runner before the vessel is filled with pig iron. In the case of a mixer without a cover, this positioning is usually achieved by use of the opening which is visible in sharp contrast due to the high temperature of the inside of the transfer vessel. If a cover is used, this method of positioning cannot be used; therefore the cover should preferably, have on the side facing away from the inside of the vessel, a contrasting mark which provides an unambiguous indication of the position and extent of the opening in the vessel when the cover is fitted to close this opening. BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will be illustrated below by way of non-limitative example with reference to the accompanying drawings, in which: FIGS. 1a to 1d are a diagrammatic representation of the method according to the invention. FIGS. 2a and 2b show a longitudinal and transverse section respectively through a typical mixer type hot metal car. FIGS. 3a to 3h show various forms of disposable cover for use in the method according to the invention, in section. FIGS. 4a to 4c show further details of various covers for use in the invention. FIGS. 5a to 5c are a top view and sectional views of one embodiment of the disposable cover. DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1a the conveyance of liquid pig iron between a blast furnace 1 and a steel making plant 2 by means of a mixer type hot metal car 3 (torpedo car) is represented symbolically. FIG. 1b show diagrammatically the method of conveyance according to the state of the art, in which the hot metal car 4 is shown in cross-section. The car is moved, after being filled with pig iron at the blast furnace (5) to the steel making plant where the pig iron is transferred to a receiver, not shown by rotating the vessel (6). The empty car is then returned to the blast furnace and filled again with pig iron (7). As shown in FIG. 1c, according to the method of the invention, a disposable cover 10 is fitted on the vessel to close the opening thereof after the vessel is filled with pig iron (8) and/or after the pig iron has been transferred to the receiver (9). In each case a cover is lost into the pig iron, at 9 when the vessel is discharged and at 11 when the vessel is recharged. FIG. 1d shows diagrammatically the variation of the temperature of the pig iron and of the refractory brick of the vessel of the hot metal car during outward journeys 5-6, 8-9, and during return journeys 6-7, 9-11. The location at the blast furnace is at the left, and the location at the steel making plant at the right. Temperature is plotted vertically. The lines 8-9-11 apply for the case where a disposable cover is fitted on the mixer car both during the outward and return journeys and the lines 5-6-7 for the case where no cover is used during both the outward and return journeys 5-6-7. It is thus shown that, when a cover is used, the temperature loss both during the outward journey 8-9 and during the return journey 9-11 is smaller than during the outward journey 5-6 and return journey 6-7 without a cover. Temperature T9, at which the pig iron is supplied to the steel works when using the cover, is higher than temperature T6 when no cover is used. Temperature T7 of the refractory lining, just before filling, when no cover is used, is lower than temperature T11 when the cover is used. FIGS. 2a and 2b show a mixer type hot metal car in a conventional embodiment comprising a torpedo-shaped transfer vessel 12, which is provided on the inside with a refractory brick 13, and which may be rotated about the horizontal longitudinal axis at both ends 14 and 15, and is supported on bogies 16 and 17. The vessel has an opening 18, around which it is protected by a plate 19 on the outside against the pig iron being poured into the vessel. This plate 19 is in most cases right up against the opening. In the preferred method of the invention a disposable cover is fitted for closing the opening, and retaining means are used to keep the cover located at the opening, particularly during movement of the car. This movement usually takes place in the open air, and the cover, which should preferably be lightweight, may easily be lifted by wind from the car if no retaining means are used. However the use of the retaining means should preferably not involve any additional operations when removing any remains of the disposable cover after filling or discharge, and when fitting a new disposable cover after filling or discharge. In the embodiment shown in FIG. 3a, the retaining means consist of pins 20 which are connected to plate 19 and which extend into holes 21 in the flat disposable cover 36. Pins connected to the disposable cover, which drop into holes in the plate, may alternatively be provided. In each of the embodiments of the disposable cover shown in FIGS. 3b to 3h the retaining means consist of a part or parts of the cover projecting into the opening and located close to or abutting the edge wall 22 of the opening. In the cover of FIG. 3b, this inwardly projecting part is in the form of a plurality of rod-shaped elements 23. In the cover shown in FIG. 3c, the part projecting into the opening is a wall structure 24 which is closed circumferentially and which at least partially protects the refractory lining of the opening of the transfer vessel while it is being filled with pig iron. In the covers shown in FIGS. 3d to 3h the part extending into the opening has an external taper (tapering towards the inside of the vessel when fitted) dimensioned so that the cover fits into the opening when located on the vessel. Whether or not combined with elastic deformability of the tapered section, this feature causes the cover to wedge in the opening when located on the vessel, and also provides the opening with the excellent sealing against heat loss to convection. FIG. 3d shows an embodiment of the tapered configuration with separate legs 25. In FIGS. 3a to 3d inclusive, the cover is shown provided with an external collar 26 extending past the edge of the opening 18, which collar at least temporarily protects the refractory lining 27 outside of the opening during the filling with pig iron. In the embodiments of FIGS. 3f to 3h the upper portion 29 of the cover which closes the opening 18 has a cup-shaped section 28 or depression which reduces the splashing of pig iron when commencing filling. In the covers of FIGS. 3g and 3h, the vertical side wall 30 of this cup portion coincides with the tapered circumferentially closed wall structure 24. The material from which the cover is manufactured must meet essentially contradictory requirements. On the one hand the cover should have a good insulation value to limit heat transmission through it. The cover should also be at least sufficiently refractory to resist the thermal loading from the liquid pig iron or the refractory brick during the outward or return journey. On the other hand, the part or parts of the cover which are carried away with the pig iron when the car is filled, or when the car is emptied into the receiver, should arrive in a pig iron bath in disintegrated form so that they will not remain as distinguishable lumps of the cover. At the same time, the cover should not give rise to undesirable additives in the pig iron and/or slag during disintegration e.g. by combustion, melting, decomposition or loss of cohesion. As shown in FIG. 3h, the cover can be reinforced with stiffener 36, e.g. a gauze to obtain a low weight, good elasticity and sufficient strength. Eyes (lugs) 37 or the like can be connected to it for use when handling the cover. However, these eyes or lugs may be anchored in the cover material even when no stiffener or reinforcement is used. In a further embodiment of the invention the cover is divided into several parts, in which case part of the cover, e.g. collar 26 and or the circumferentially closed wall structure 24 is retained when the mixer is filled and can be re-used. A hole is made in the wall portion 28 which closes opening 18 for the purpose of filling the vessel, preferably by the effect of the pig iron on the cover when filling starts. This hole comprises at least part of the wall portion 28. This effect of the pig iron is the mechanical action of the impulse of the jet of pig iron from the blast furnace runner, which breaks a hole through or the thermal action of the heat of the liquid pig iron on the material of the cover which burns or melts a hole or by a combination of both these effects. The cover of FIGS. 4a to 4c has for this purpose an at least local weakening. In the embodiment shown in FIG. 4a, this consists of a wall thinning 30, in FIG. 4b it is a shear plate 31, and in FIG. 4c it consists of a cap 32. The embodiments of FIGS. 4b and 4c are well suited for the m