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NEW DESIGN OF MACHINE WRENCH FOR DRILLING AND DRIVING PIPES
At the All-Union Research Institute of Petroleum Machinery investigations were carried out revealing the regularities of the transmission of torque by machine wrenches based on different schemes. It was thereby established that the clamping forces of the jaws exerted by the machine wrench at torques of 30-40 kN'm suffice for transmitting much higher torques (>80 kN'm). In connection with that it therefore becomes possible to reduce the weight of the wrenches and increase their reliability by reducing the intensity of the clamping of the spanner jaws on the pipes in proportion to the increase of torque. Of course, at the initial stage of loading a clamping force has to be ensured that makes slippage of the wrench impossible. However, machine wrenches of traditional design do not ensure the necessary regularity of the change of forces in the gripping links of the wrench. The characteristics of the intensifying mechanisms of wrenches based on different schemes are presented in [i].
It should be borne in mind that contact of the wrench with the pipe occurs at large values of the angles of rotation ~ of the lever. Then, as the drawing force on the lever of the wrench increases, the angle ~ becomes smaller, i.e., the process of tightening the thread proceeds from right to left (see Fig. i).
The most efficient combination of intensifying mechanisms can be obtained in wrenches with link gear and hinged mechanism. When the pipe is gripped first, the link mechanism acts (curve i); its zone of action is limited by the size of the slit in the lever. Then comes the transition to operation by the hinged four-link mechanism (curve 2) ensuring the highest coefficients of intensification. When the end face of the lever comes up against the final gripping link, intensification proceeds by the scheme of the crank and connecting rod mechanism (curve 4) with a connecting rod of variable length. Thus, in the case under consideration, tightening of the wrench links on the pipe begins at an intensification coefficient i = 18-20, which increases to i = 42-45, and ends with i = 12-13.
With wrenches with hinged scheme the process of tightening ends with the coefficient of intensification i > 25 (curves 2, 3). This also explains why these wrenches weigh 20%[2] more than wrenches with link gear and hinged mechanism.
Another substantial advantage of the link gear and hinged wrench should be mentioned: the wider range of working angles of rotation of the lever: -15 < e < 30 .
For wrenches with the hinged scheme -5 < ~ < 18 ~because of the unreliable gripping with i < 18-20 at the onset of the process and the better operation of such wrenches by the scheme of the crank and connecting rod mechanism (curve3).
The results of our investigations were made the basis for working out the multihinge machine wrench KMB 108-2112 for drilling pipes with torque limiter [3]. The special feature of the design of these wrenches consists in the reduction of the coefficient of intensification to one-half or one-third when the process of tightening the wrench on the pipe is concluded; this is the result of a braking force being applied to the end face of the lever by means of a special torque limiter.
The wrench operates on the link gear and hinge mechanism scheme. The torque limiter, a part with a groove of wedge-shaped section, is hinged to the drawing link of the gripping part of the wrench. On the end face of the lever there is a rack with the same section as the groove of the torque limiter.
The wrench begins to operate by the link gear scheme; when the motion is limited in the slide groove, it operates by the scheme of the hinged four-link mechanism, and when approximately half the maximal drawing force is attained, it operates by a scheme where the rack of the lever fits tightly into the groove of the torque limiter.
Thanks to the effective braking of the wrench lever at the last stage, it forms with the drawing link of the gripping part a two-armed lever with the ratio of the arms approximately equal to three, which corresponds to the coefficient of intensification of the fifth scheme (see Fig. i). Thus in the wrench KMB 108-212 a rational combination of t]he operating regimes was effected: with large intensification (i <_ 45) at the beginning of the process with small drawing loads on the lever (to attain reliable cohesion between the wrench and the pipe) and with considerable reduction of the intensification when high drawing loads are attained (to prevent overloading of the wrench). Strain-gauge measurements showed that in that case the maximal stresses in the links of the wrench are reduced by one third to one half.
A prototype of the wrench KMB 108-212, calculated for a nominal torque of 80 kN~ was tested on a test bench of the Azerbaidzhan Institute of Petroleum Machinery with a torque of 207.5 kN-m. The efficiency of the wrench was not impaired in any way. In 1985 series production of the wrenches KMB 108-212 started. However, production to full capacity of these tools is prevented by the unstable quality of cast blanks for the wrench.
A FEED UNIT FOR DRILLING MACHINES
The feed units of drilling machines feed the drill mechanism, drill rod, and bit towards the face during drilling, and also raise and lower the drill rod.
Mechanical feed units with drive from a pneumatic motor [1] are small and can develop large feed thrusts. However, they have certain drawbacks: the feed velocity is low, which increases the time required for auxiliary operations; the apparatus is complicated and insufficiently reliable in use; and the pheumatic motor is noisy. Pneumatic piston feed units [2] are simple in design and reliable in use, and give elasticity of the feed, reducing wear on the bit and permitting an increase in the productivity of drilling. However, they are large, because the thrust developed depends on the area of the piston which is acted on by compressed air at a comparatively low pressure of 5-6 kg/cm . Nevertheless, the full rated feed thrust is quite rarely used (for example, in the last few meters of a deep borehole).
With the aim of improving the operational qualities of drilling machines, we have developed a new type of pneumatic piston feed unit. Its essential feature is that the air pressure in the feed cylinder can be several times greater than that in the air mains. This is achieved by means of a pressure converter consisting of several pistons and cylinders in series.
Figure 1 shows a schematic diagram of the feed unit. The working parts comprise feed cylinder 1 with piston 9 and rod 3. The pressure converter consists of cylinder 4 with freely moving piston 5 and several single cylinders 6 with tappets 7. The rod of each tappet passes through a gland in the end wall and freely bears on the head of the preceding tappet. Air is distributed by piston valve 8. The elements of the system are connected by air ducts, one of which contains back valve 9, and another cut-off valve 10. The feed unit is controlled by means of tap 11.
The system works as follows. Compressed air from the mains passes through inlet tap 11 and valve 9, and arrives in the left-hand cavity of cylinder 1, where it bears on piston 2, creating a thrust. Simultaneously air passes into cylinder 4, and also through valve 10 and annular space a in piston valve 8 into the right-hand cavities of cylinders 4 and 6. The left-hand cavities of cylinders 6 are always in communication with the atmosphere. Piston 5 and tappet 7 move to the left, and the forces created by the air pressures on each of them are added together. The air in the left-hand cavity of cylinder 4 is compressed to a pressure greater than that in the mains (the maximum pressure in this cavity depends on the number of cylinders 6). The high-pressure air passes through annular space b and reaches feed cylinder 1, increasing the feed thrust.
Approaching its extreme leftward position, piston 5 opens a port to control duct c into which air at mains pressure comes from the right-hand cavity of cylinder 4. The air bears on the right-hand face of piston valve 8, the left-hand end of which is at this time freed from load owing to escape of air via a small hole k (the control duct d is now covered by piston 5). The piston valve moves to the left.
When the piston valve is in its leftward position, feed cylinder 1 is disconnected from the pressure converter. The right-hand cavities of cylinders 4 and 6 are connected to the exhaust via annular space e. Air from the mains passes through annular space a and arrives in the left-hand cavity of cylinder 4, causing piston 5 and tappet 7 to move to the right. When piston 5 reaches its extreme right-hand position, it opens duct d and mains-pressure air enters the left-hand end of piston valve 8. At this time duet c is covered and the right-hand end of the piston valve is released from pressure. The piston valve moves to the right, and then the cycle is repeated until the pressure in feed cylinder 1 reaches its maximum value. The operation of the converter is then automatically stopped, and is recommenced as the air pressure in the feeder fails owing to forward movement of piston 2 and increase in the volume of the working cavity of the feed cylinder. Thus the system operates at high feed pressures.
If the resistance offered to rod 3 is small, the piston moves in the cylinder at low pressures. Then the pressure of the air passing via duet f to piston valve 10 cannot overcome the force of the spring and air from the mains is cut off from the converter. On the other hand, if the resistance offered to the rod increases so much that direct feed via valve 9 cannot effect operation of the feeder, then the pressure in the working cavity increases to mains pressure and will be sufficient to move valve 10 to the right, so that it admits air to the converter.
The presence of direct feed (via the back valve) and of the piston valve, which cuts off the pressure converter, permits drilling to be effected in most eases without the converter; increased pressure is used only at the end of a deep borehole. By adding successive interchangeable cylinders with tappets, it is possible to build up the feed unit to any maximum feed thrust required by the drilling conditions.
In principle, the feed unit with pressure converter can be hydraulic instead of pneumatic. The pressure step up converter might find uses in other pneumatic devices with low air consumption; for example, attachments to machine tools.
鉆床的補(bǔ)給單位
鉆床的補(bǔ)給單位補(bǔ)給鉆頭機(jī)械裝置,鉆桿, 而且在鉆孔期間向面咬, 以及升起并且降低鉆頭桿。
機(jī)械的補(bǔ)給單位與來自一個(gè)空氣的電動(dòng)機(jī)的駕駛很小而且能發(fā)展大的補(bǔ)給推力。然而, 他們也有一些缺點(diǎn)：補(bǔ)給速度低, 增加了對(duì)附加的操作的必需時(shí)間；裝置在使用中復(fù)雜，不夠可靠；而且電動(dòng)機(jī)噪聲大?？諝獾幕钊a(bǔ)給單位設(shè)計(jì)簡(jiǎn)單，使用中靠, 而且補(bǔ)給柔性, 減少了刀尖的磨耗而且增加了鉆孔的生產(chǎn)力。但是，他們也很大，因?yàn)橐揽炕钊拿娣e推動(dòng)活塞把空氣壓縮到5-6 一個(gè)比較低的壓力。然而，充足的定格補(bǔ)給推力卻很少地被使用。
為了提高鉆床的操作性質(zhì)，我們發(fā)明了一個(gè)新類型的空氣活塞補(bǔ)給單位。它的主要特征是在補(bǔ)給氣缸的氣壓比在空氣輸電干線中的大得多。這藉由壓力轉(zhuǎn)爐被達(dá)成系列中有一些活塞和氣缸。
圖 1 表示一個(gè)補(bǔ)給的概要線圖單位。工作零配件用活塞 9 和桿 3 包含補(bǔ)給氣缸 1。壓力轉(zhuǎn)爐包含氣缸 4、移動(dòng)活塞 5 和一些帶有挺桿 7的單一氣缸 6 。每個(gè)挺桿的桿最后經(jīng)過一個(gè)填函蓋鑄壁負(fù)擔(dān)自由地與前述挺桿的冒口?？諝獗换钊y 8 分配。系統(tǒng)的機(jī)械要素被導(dǎo)氣管連接, 他含有背后閥 9 、和另外的一個(gè)停氣閥 10。
補(bǔ)給單位由水栓 11 控制。
系統(tǒng)工作次序如下。來自輸電干線的壓縮空氣經(jīng)過進(jìn)模口水栓 11 和閥 9, 抵達(dá)氣缸 1 的左手方模穴。同時(shí)地空氣獲準(zhǔn)進(jìn)入氣缸 4, 以及經(jīng)過閥 10 和在活塞閥 8 中的環(huán)隙進(jìn)入氣缸 4 和 6 的右手模穴之內(nèi)。 左手方模穴與活塞 2 有關(guān),他創(chuàng)造了一個(gè)推力。而氣缸 6 的左手方模穴總是在與大氣溝通 ?；钊?5 和挺桿 7移動(dòng)到左邊, 使氣壓變大。在氣缸 4 的左手方模穴的空氣被壓縮比在輸電干線中的壓力大(這一個(gè)模穴中最大的壓力仰賴氣缸 6 的數(shù)目)。 高壓的空氣經(jīng)過環(huán)隙 b 和延伸補(bǔ)給氣缸 1,增加補(bǔ)給推力。
在它的最左的位置, 活塞 5有一個(gè)口用導(dǎo)管c控制由氣缸 4 的右手模穴進(jìn)入的空氣。空氣進(jìn)入活塞閥 8 的右手面貌, 在沒有負(fù)載的左手方端防止空氣由一個(gè)小孔 k 逃脫.(控制導(dǎo)管 d 現(xiàn)在被活塞 5 復(fù)蓋)。活塞閥移動(dòng)到左邊。
當(dāng)活塞閥在它的左方位中的時(shí)候，補(bǔ)給氣缸 1 從壓力轉(zhuǎn)爐被分離。氣缸 4 和 6 的右手模穴經(jīng)由環(huán)隙 e 排氣。來自輸電干線的空氣經(jīng)過環(huán)隙一抵達(dá)氣缸 4 的左手方模穴, 讓活塞 5 和挺桿 7 移動(dòng)到右邊。當(dāng)活塞 5 移動(dòng)到最右邊時(shí)，由導(dǎo)管 d 空氣由導(dǎo)管 d 進(jìn)入活塞閥 8 的左端. 這時(shí)導(dǎo)管c 被復(fù)蓋，活塞閥的右端壓力被釋放?；钊y移到右邊, 繼續(xù)循環(huán)直到補(bǔ)給氣缸1的氣壓達(dá)到最大。轉(zhuǎn)爐自動(dòng)停止,當(dāng)送料器的氣壓沒有到達(dá)活塞 2時(shí)，轉(zhuǎn)爐重新開始并增加補(bǔ)給氣缸的工作模穴的容積。這樣系統(tǒng)就在高的補(bǔ)給壓力下操作。
如果提供給桿 3 的阻力很小, 在低的壓力氣缸中的活塞就會(huì)移動(dòng)。然后空氣的壓力經(jīng)由導(dǎo)管 f 到達(dá)活塞閥 10，防止空氣從轉(zhuǎn)爐中走開。另一方面，如果阻力過大，直接導(dǎo)致氣壓經(jīng)過閥 9 不能夠進(jìn)行送料器的操作，那么在工作模穴的壓力就會(huì)增加到輸電干線壓力，而且將會(huì)讓閥 10 充份移動(dòng)到右邊，從而使空氣進(jìn)入轉(zhuǎn)爐。
直接補(bǔ)給和能切斷壓力轉(zhuǎn)爐的活塞閥的出現(xiàn),，使得鉆床在沒有轉(zhuǎn)爐的的情況下更容易實(shí)現(xiàn)增加的壓力只在一個(gè)深洞結(jié)束的時(shí)候被用。通過增加連續(xù)的可互相交換的挺桿氣缸，可以建立補(bǔ)給單位達(dá)到必需的任何的最大補(bǔ)給推力。
大體而言 , 擁有壓力轉(zhuǎn)爐的補(bǔ)給單位可能是水力的改為空氣的。壓力階段的轉(zhuǎn)爐因?yàn)榈偷目諝庀牧靠赡茉谄渌目諝庋b置中得到使用； 舉例來說, 工作機(jī)的輪磨配件。