Bài giảng Kỹ thuật nâng & vận chuyển - Chương 4: Các thiết bị phanh hãm (arresting gear and brakes)

KYÕ THUAÄT NAÂNG - VAÄN CHUYEÅN

CHÖÔNG IV CAÙC THIEÁT BÒ PHANH HAÕM (ARRESTING GEAR AND BRAKES)

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Chapter IV 1

1. MUÏC ÑÍCH:

-They stop the load and hold it when applied to the hoisting motion or bring the relevant mechanisms at rest within specified braking distances as this is the case on traveling and slewing motion

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Chapter IV 2

2. PHAÂN LOAÏI:

 Döïa vaøo caáu taïo boä phaän laøm vieäc (contruction):

Phanh maù. Phanh ñai. Phanh ñóa. Phanh noùn.

}

Hôïp thaønh phanh aùp truïc (coù maët ma saùt taùch rôøi hay khoâng taùch rôøi).

 Döïa vaøo nguyeân taéc hoaït ñoäng (operating principle) :

Phanh töï ñoäng (automatic) Phanh ñieàu khieån.( controlled)

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Chapter IV 3

2. PHAÂN LOAÏI (tt):

 Döïa vaøo chöùc naêng (the purpose the brake serves):

Phanh döøng cô caáu ôû cuoái chuyeån ñoäng.( stopping brakes) Phanh giôùi haïn vaän toác, nhöng khoâng giöõ vaät.( regulating brakes)

 Theo tính chaát cuûa söï taùc ñoäng löïc ñieàu khieån phanh (the mode of applying the brakes-operating force):

Phanh thöôøng ñoùng.( normally -set brakes) Phanh thöôøng môû.( normally-released brakes) Phanh tổng hợp. (combination brakes)

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Chapter IV 4

3. CÔ CAÁU KHOÙA DÖØNG

(Arresting gear)

 Purpose - Arresting gears are the means of sustaining the load which do not interfere with the hoisting but prevent it from coming down due to gravity

- Arresting gear in general fall into two basic kinds which are the ratchet-and-pawl arrangement and Back-stopping roller clutch

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Chapter IV 5

3.1 CÔ CAÁU BAÙNH XE COÙC (Ratchet- and- pawl arrangement)

 Nguyeân lyù laøm vieäc:  Cheá taïo:

Baùnh xe: vaät lieäu gang 18-36, theùp (ñuùc). Con coùc: theùp 45↑, 40X.

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Chapter IV 6

3.1 CÔ CAÁU BAÙNH XE COÙC (Ratchet- and- pawl arrangement)

 Caáu taïo:

Taêng cöôøng söï lieân keát (ñaët vaøi con coùc (a) Goùc 900 =>

=b/m lớn khi coù

va ñaäp maïnh. Coù con coùc giaûm oàn (b)

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Chapter IV 7

3. CÔ CAÁU BAÙNH XE COÙC(tt):

 Tính toaùn.

Xaùc ñònh modun: m

}

hoaëc

 neáu m > 6 => Kieåm tra [q]  neáu m < 6 => Kieåm tra uoán =>

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Chapter IV 8

3. CÔ CAÁU BAÙNH XE COÙC(tt):

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Chapter IV 9

4. PHANH MAÙ (Block brakes)

Block brakes used in hoisting installation exit in a great number of types -In most case they consist of two blocks arranged at diametrically opposite points of a drum and operated by levers -Braking is effected due to friction setup fitted to lever of braking system on the trolley or bridge

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Chapter IV 10

4. PHANH MAÙ(tt):

a. Phanh moät maù (single- block brake)

Momen phanh:

Nhaän xeùt: b = 0 => P = const.

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Chapter IV 11

4. PHANH MAÙ(tt)-hai maù-

 Ñaëc ñieåm caáu taïo caàn .

Do N1 S1

N2 => S2

=> Löïc uoán truïc S

Ñeå truïc phanh khoâng uoán:

S = 0 => b = 0.=> Phanh

coù caàn

thaúng.

 Momen phanh:

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=> ÔÛ phanh caàn thaúng =>

Chapter IV 12

4. PHANH MAÙ(tt)

b. Phanh 2 maù- duøng ñoái troïng

 Löïc ñoùng phanh:

 Löïc ñoùng phanh:

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Chapter IV 13

4. PHANH MAÙ(tt):

c. Phanh nam chaâm ñieän töø: (Short-stroke electromagnet brake)

1. Loø xo neùn chính. 2. Loø xo neùn phuï. 3. Nam chaâm ñieän töø. 4. Ñai oác ñieàu chænh loø xo neùn chính. 5. OÁc ñieàu chænh khe hôû maù phanh.

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Chapter IV 14

4. PHANH MAÙ(tt):

 Nguyeân lyù laøm vieäc: Phanh thöôøng ñoùng

Khoâng coù ñieän : loø xo 1 bò neùn , seõ coù löïc ñaåy veà hai phía: ñaåy voû hoäp 7 veà traùi keùo caàn phaûi ñoùng maù phaûi; ñaåy ñai oác 4 (töùc truïc loø xo ) veà phaûi keùo caàn traùi ñoùng maù traùi => phanh ñoùng.

Khi coù doøng ñieän vaøo nam chaâm ñieän tö ø: seõ huùt caàn phaûi vaø ñoàng thôøi ñaåy truïc loø xo sang traùi => môû phanh ( ñoàng thôøi vôùi ñoäng cô laøm vieäc cuûa cô caáu).

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Chapter IV 15

4. PHANH MAÙ(tt):

 Öu ñieåm:

↑.

Söûa chöõa nhanh.

 Nhöôïc ñieåm:

Tuoåi thoï thaáp. Va ñaäp khi nam chaâm laøm vieäc.

=> Khaéc phuïc coù phanh thuûy löïc.

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Chapter IV 16

4. PHANH MAÙ(tt):

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Chapter IV 17

4. PHANH MAÙ(tt):

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Chapter IV 18

5. PHANH ÑAI (BAND

BRAKES)

 In band brakes, the braking torque is

obtained due to friction of a flexible band over the surface of a brake wheel.

 Band brakes are designed using the well-

known Euler’s formula for a flexible filament which provides the relationship between the maximum Sv tension and the minimum tensions Sr in the band sides

Sv= Sr. ef

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Chapter IV 19

5. PHANH ÑAI (BAND BRAKES)

a.

Phanh ñai ñôn giaûn. ( the simple band brake)

1. 2. 3. 4. 5.

Baùnh phanh Ñai baèng theùp Caàn Nam chaâm ñieän tö Ñoái troïng

The maximum tension on the tight side of the band come on fixed point, rendering the brake suitable for use with the wheel always rotating in the same direction

The single band is used on motion where the



braking torque varies with the direction of rotation, as in the hoisting mechanism Nguyeân lyù laøm vieäc:

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Chapter IV 20

5. PHANH ÑAI (BAND BRAKES)

a. Phanh ñai ñôn giaûn (tt) ( the simple band brake)  Nguyeân taéc : (Enler)

Nhaän xeùt: ñeå Mf ↑

=> S1↑ => ↑ ; f ↑

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Chapter IV 21

5. PHANH ÑAI (tt):

 Löïc ñoùng phanh:

laàn => Cô caáu naâng.

 Nhaän xeùt: K thay ñoåi ef  Löu yù vôùi K xaùc ñònh:

M thuaän chieàu kim ñoàng hoà > M ngöôïc chieàu kim ñoàng hoà

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Chapter IV 22

5. PHANH ÑAI (tt):

b. Phanh ñai vi sai. ( Differential band brake)  Momen phanh:

vôùi

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Chapter IV 23

5. PHANH ÑAI (tt):

 Nhaän xeùt:

=> Mf → : töï ñoùng

 Öu ñieåm: cho pheùp K  Nhöôïc ñieåm:

 Töï khoùa -> va ñaäp.  Mf thay ñoåi khi thay ñoåi chieàu quay giaûm nhieàu

laàn.

 Traùnh töï haõm: a1 > a2. ef

[a1 =(2,5 3)a]

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Chapter IV 24

5. PHANH ÑAI (tt):

c. Phanh ñai toång hôïp.



( Reversible band brake) Löïc ñoùng phanh.



Tröôøng hôïp: a1 = a2 = a



Nhaän xeùt:

a1 = a2 => Mf = const => Cô caáu di chuyeån, quay. a1 < a2 => cô caáu naâng.

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Chapter IV 25

5. PHANH ÑAI (tt):

 Keát luaän:

Kmin : vi sai. Kmax: toång hôïp. Vi sai coù tính chaát töï haõm => cô caáu duøng tay. Ñôn giaûn, toång hôïp => cô caáu naâng. Toång hôïp (a1 = a2 ) : cô caáu di chuyeån.

 Öu nhöôïc ñieåm:

Öu: ñôn giaûn, goïn. Nhöôïc:

Uoán truïc (S1 + S2) Phaân boá aùp löïc khoâng ñeàu -> moøn. Tuoåi thoï thaáp.

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Chapter IV 26

5. PHANH ÑAI (tt):  Phanh ñai taùc duïng hai chieàu.

 Ñaëc ñieåm:

Ñaàu ñai coù Smax luoân coá ñònh. Löïc taùc duïng ñoùng phanh luoân ôû ñaàu Smin Ñieåm töïa tay ñoøn thay ñoåi khi thay ñoåi chieàu quay. Löïc ñoùng phanh giaûm so vôùi phanh toång hôïp.

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Chapter IV 27

5. PHANH ÑAI (tt):

 Keát luaän

Öu ñieåm:

Ñôn giaûn, goïn, Mf ↑ = ↑ Thöôøng söû duïng phanh ñai ñôn giaûn.

Nhöôïc ñieåm:

Gaây uoán truïc. AÙp löïc phaân boá khoâng ñeàu. (-> ef ) Mf khoâng oån ñònh (f thay ñoåi laøm Mf thay ñoåi ) Ñai phanh ñöùt => nguy hieåm => ñoä tin caäy keùm hôn phanh maù

=> phanh maù ñöôïc söû duïng nhieàu hôn phanh ñai.

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Chapter IV 28

6. PHANH AÙP TRUÏC (Thrust brakes)

A salient feature of thrust brakes is that the load require to produce the braking torque is directed along the axis of the brake shaft

a. Phanh noùn.(Cone brake)



Caáu taïo: 1. Truïc 2. Baùnh noùn (laép treân truïc baèng

then).

3. Baùnh coùc + maët coân (laép loàng



khoâng). 4. Con coùc. Nguyeân taéc laøm vieäc:

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Chapter IV 29

6. PHANH AÙP TRUÏC (Thrust brakes) tt

 Kieåm tra aùp löïc:

Keát luaän:

v toác ñoä thay ñoåi phuï thuoäc D => moøn khoâng ñeàu. (1 1,5 kg/cm2 [p] laáy nhöng khoâng quaù 2 2.5 kg/cm2 )

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Chapter IV 30

6. PHANH AÙP TRUÏC (Thrust brakes) tt

 Tính löïc ñoùng phanh: Ñieàu kieän phanh:

Treân hình veõ:

=> Keát luaän:

=> dính coân)

(f = 0,3

K ( => = 150 => f ↑ 0,4).

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Chapter IV 31

6. PHANH AÙP TRUÏC (Thrust brakes) tt

b. Phanh ñóa ( disc brake)



Laø phanh noùn khi = 900.

 Muïc ñích:

K khi taêng caëp maët tieáp xuùc.

AÙp suaát beà maët:

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Chapter IV 32

6. PHANH AÙP TRUÏC (Thrust brakes) tt

 Vôùi Mf cho tröôùc: giaûm K baèng phanh nhieàu ñóa.

Coù z caëp maët => Momen 1 maët:

Löïc voøng:

=> Löïc ñoùng phanh:

 Keát luaän: K Z laàn so vôùi chæ coù 1 caëp tieáp xuùc.

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Chapter IV 33

6. PHANH AÙP TRUÏC (Thrust brakes) tt

 Toång keát:  Nhöôïc ñieåm so vôùi maù vaø ñai:

Keát caáu phöùc taïp hôn. Beà maët moøn khoâng ñeàu.

 Ít duøng trong ngaønh cheá taïo caàn truïc.  Söû duïng döôùi daïng phanh aùp truïc töï ñoäng

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Chapter IV 34

6. PHANH AÙP TRUÏC (Thrust brakes) tt

 Brakes for lowering loads also referred to as weight- operated or load brakes are widely employed in hand – operated hoists and some power –driven installation.

 The purpose they serve is to stop and hold the load

suspended by applying a torque which is proportional to the weight of the load hoisted  The braking torque is set automatically by the

torque from load

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Chapter IV 35

6. PHANH AÙP TRUÏC (Thrust brakes) tt

c. Phanh aùp truïc töï ñoäng coù maët ma

saùt khoâng taùch rôøi.

(Load brakes operating at a constant

friction surface drag both in lowering and hoisting) 1. Baùnh coân lieàn moät khoái vôùi truïc vít. 2. Baùnh coùc khoeùt maët coân beân trong. 3. Con coùc. 4. Tay quay.

 Löïc ñoùng phanh: löïc doïc truïc cuûa truïc vít

döôùi taùc duïng cuûa troïng löôïng vaät naâng = > Q = const => maët phanh luoân kheùp kín khi naâng cuõng nhö khi haï (maët ma saùt khoâng taùch rôøi).

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Chapter IV 36

6. PHANH AÙP TRUÏC (Thrust brakes) tt

 Naâng: döôùi taùc duïng Q (1) eùp (2) thaønh moät khoái

quay theo chieàu naâng caû heä thoáng quay coùc khoâng caûn trôû chuyeån ñoäng.

 Döøng: ngöøng ngay, coùc khoâng cho pheùp cô caáu

quay theo chieàu haï.

 Haï vaät: quay theo chieàu haï Mquay thaéng Mf dö

giöõa beà maët coân => maët laøm vieäc bò maøi moøn => chæ duøng trong cô caáu quay tay.

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Chapter IV 37

6. PHANH AÙP TRUÏC (Thrust brakes) tt

 Tính toaùn:  Phanh duøng trong vaät ñeå taïo momen phanh => thieát keá

phanh ñuû ñieàu kieän => tìm goùc nghieâng baùnh noùn.

 Momen phanh caàn thieát:

 Töø ñieàu kieän goùc noùn

(baøi phanh noùn).

 Goùc

lôùn hôn goùc ma saùt cuûa maët noùn ñeå traùch dính.

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Chapter IV 38

6. PHANH AÙP TRUÏC (Thrust brakes) tt

 Löïc ñoùng phanh K laø löïc voøng treân baùnh vít Pbv , maø

Q thay ñoåi

Pbv thay ñoåi -> Mbv thay ñoåi

tæ leä thuaän Q.

 => Löïc ñoùng phanh K vaø Mf

laáy heä

 => Tính chaát töï ñieàu chænh cuûa phanh => laáy thaáp (1,2).

soá an toaøn

 Khi haï vaät momen haï phaûi thaéng momen cho.

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Chapter IV 39

6. PHANH AÙP TRUÏC (Thrust brakes) tt

c. Phanh aùp truïc töï ñoäng coù maët ma

saùt taùch rôøi.

(Load brakes operating at a reduced

friction surface in lowering.) 1. Ñóa laép coá ñònh treân truïc. 2. Baùnh coùc quay töï do. 3. Con coùc 4. Baùnh raêng coù maët bích ñaët loàng

trong ñoaïn ren. 5. Vít ñieàu chænh.

 Phaïm vi söû duïng: cô caáu naâng daãn ñoäng

baèng T vaø M.

Caáu taïo: chieàu ren ñöôïc choïn sao cho döôùi taùc duïng cuûa momen do

troïng löôïng vaät qua boä truyeàn baùnh raêng 4 thì baùnh raêng phaûi dòch chuyeån theo chieàu ren veà beân traùi eùp chaët baùnh coùc (2) vaø ñóa (1).

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Chapter IV 40

6. PHANH AÙP TRUÏC (Thrust brakes) tt

 Nguyeân taéc laøm vieäc:

Naâng: truïc 6 quay theo chieàu naâng con coùc khoâng caûn trôû chuyeån ñoäng. Döøng: döôùi taùc duïng cuûa troïng vaät => 1+2+4 baèng moät khoái lieân keát chaët baèng ma saùt => con coùc caûn trôû chuyeån ñoäng baùnh coùc 2 => vaät döøng (treo). Haï: truïc 6 quay: w6 => baùnh raêng naèm yeân treân truïc: w4 = 0

=> Noù theo chieàu ñoaïn ren taùch khoûi baùnh coùc =>

maát K.

=> Vaät rôi töï do: w4 ↑ (luùc ñaàu w4 < w6 ). => Rôi coù gia toác : w4 > w6 => baùnh raêng theo ren

eùp vaøo baùnh coùc => cô caáu döøng

veà traùi => w4 = 0.

=>(6) vaãn quay => quaù trình laëp laïi.

Toùm laïi: haï vaät laø loaït quaù trình rô töï do vaø döøng => ñcc

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Chapter IV 41

 ANY QUESTIONS ?

 ………..

 THANK YOU

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Chapter IV 42