《钻孔机的进给单位dt.doc》由会员分享，可在线阅读，更多相关《钻孔机的进给单位dt.doc（5页珍藏版）》请在金锄头文库上搜索。
1、外文翻译A FEED UNIT FOR DRILLING MACHINESN. N. Esin and . G. Chernilov UDC 622.233.056 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 s
2、mall 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 pneumatic motor is noisy.Pneumatic piston feed units 2 are simp
3、le 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 pLton which is acted on by compressed air at a comparatively low pr
4、essure of 5-6 kg/cm 2. Nevertheless, the full rated feed thrust is quite rarely used (for example, in the last few meters of a deep borehole). thrusts.However ，With the aim of improving the operational qualities of drilling machines, we have developed a new type of pneumatic piston feed unit. Its es
5、sential 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 compr
6、ise 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
7、 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 . The system works as follows. Compressed air from the mains passes through inlet tap 11 and valve 9, and arrives i
8、n 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 commu
9、nication 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
10、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 cylinde
11、r 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 ductd is now covered by piston 5). The piston valve moves to the left.When the piston valve is in its leftward position, feed
12、 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 ri
13、ght. Wen 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 i
14、s 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 9 and increase in the volume of the working cavity of the feed cyli
15、nder. 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 pres-sure 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
16、 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 th
