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A machine for slitting plastic pipes
J. agric. Engng Res. (1966) 11 (3) 230-232
A Machine for Slitting Plastic Pipes VV.
T.B.~ARCHANT*
1. Introduction Rigid extruded p.v.c. drain tube in approximately 16 ft lengths has been used widely in Holland, mainly in conjunction with chain type trench excavating machines, with claimed overall economies of up to 20 %over clay pipe on handling and transport costs.' In this country Ede" has examined the feasibility of in-situ cast drains of porous concrete and Ede' and Boa" have used subsoiling tines to lay latch-up pipe made from p.v.c. foils. More recently this work has been extended, using similar laying equipment, to include the use of extruded p.v.c. tube made flexibleby corrugations . or slitting and thickwall polythene pipe. This note describes a laboratory machine for slitting extruded p.v.c, pipe" to render it both coilable and porous. It was able to process pipe of from 1·5 to 3·0 in dia, at pitches from 1·5 to over 6 in and its capacity when working at a pitch of 2·6 in was approximately 180 ft/h. A 300 ft length of a typical pipe (2,6 in o.d. with walls 0·04 in thick) slit with this machine forms into a coil 12 in wide on a mandrel of 48 in dia and with an outside diameter of 78 in, weighing 85 lb. The hydraulic performance of this pipe has been investigated by Youngs." It was found to be slightly better than that of wrapped 4 in clay tile drain, only half as good as that of a fully permeable drain tube, but nearly twice as good as the N.LA.E. latch-up p.v.c. foil liner. 4 It was found that slitting reduced the resistance of the pipe to compressive loads by less than 10 % but, as p.v.c. tends to be notch sensitive, the pipe was more likely to shatter. However, a total of 1600 ft of pipe have been successfully laid for evaluation purposes at VVrest Park and two other sites.
sides of the plane of the neutral axis of bending of the pipe, each slit extending to that plane at an angle 45° to the axis. The slits are made at a pitch of 1 pipe diameter and staggered by a t pitch between the two sides of the pipe. Although a commercial slitting machine would have to work in tandem with an extruder, moving along with the pipe in the manner of a flying cut-off saw, this machine is stationary and intermittently indexes the pipe past a pair of swinging circular saws. The pipe is supported horizontally in the working zone of the machine by two pairs of spring-loaded diabolo rollers (A) and is manipulated by two pairs of solenoid-operated clamps, one sliding (B) and the other stationary (C). Each 3t in dia slitting saw (D) is carried on an extension of a parallelogram linkage (E) so that it describes a curved path through the pipe about a centre remote from its cut. This ensures that the saws do not foul when the pipe is cut without stagger and also reduces the depth of engagement and hence the diameter of saw required. The two saw linkages are normally displaced axially relative to each other by a t pitch and are inclined to the pipe at equal and opposite angles of 45°: the saws swing in vertical planes perpendicular to each other. The movements of the saws and one clamp are derived from and synchronized by a combined two-lobed cam and two-throw crankshaft (F) with pins at 90°. The indexing mechanism consists of the sliding solenoid-operated clamp connected by a linkage (G) with a 1·5 to 6·0 in range of stroke adjustment to a cam follower (H) running on the periphery of the two-lobed cam. The cam profile is designed to give two lifts and falls of 3 in per revolution with short dwell periods at the transition points. The lift periods occupy 120° of cam movement followed by 10° of dwell and 40° of return movement and a further 10° dwell in each half revolution. The 2. Description of the machine The machine (Fig. 1) produces two sets of cam is made double-sided over the two return parallel slits perpendicular to and on opposite sections. Synchronization between movements of the saws and of the sliding clamp is obtained by • Cultivation Department, N.I.A.E. 230
231
W. T. B. MARCHANT
Fig. 1. The pipe slitting machine
making the 400 cam return movement coincide with the 200 of crank movement to each side of inner and outer dead centre positions, at which both saws arrive at the same instant. The length and geometry of the connecting rods are chosen to ensure that these saws are clear of the pipe over the 40° of crank movement, thus enabling the pipe to be indexed forward in readiness for cutting the next pair of slits. The solenoid clamps are opened and closed by a microswitch actuated by a second cam coaxial with the crank shaft and switching takes place during the appropriate 10° dwell period. Two independently switched electric motors are used: one (J) rated at t hp at 3000 rev/min drives the saws at a nominal cutting speed of 10 000 ft/min through flat belts and flexible shafts, the other (K) controls the traverse of the saws and drives the crankshaft at 7 rev/min through a small worm gear and double chain reduction. It was considered desirable that the saws should be running at full speed and clear of the pipe before the traverse was either started or stopped; this was achieved by operating a second microswitch from the solenoid switch cam which continues to feed current from the saw
motor circuit to the traverse motor until the saws are at either the inner or outer dead centre positions. In an emergency both switches (L) can be operated to stop the traverse and saws. The whole machine was normally covered by a hinged mesh guard fitted with an isolator switch (M) to cut out the saws in the event of the guard being lifted when they are running. 3.
Operation The slitting machine was used to prepare pipe for two trials undertaken for the Field Drainage Experimental Unit oftheM.A.F.F. and for a small area of clay land at Wrest Park. As it was never possible to set up the machine in line with an extruder, pipe was fed into the machine in lengths of 24 ft, thus time was spent joining successive lengths and the theoretical throughput of 180 ft/h was not achieved. As long as the pipe was reasonably straight the indexing mechanism worked satisfactorily, but where warped pipe was being cut, it was necessary for the operator to help the pipe through the machine. It is considered that further investigation would be needed to find the best type of saw for in thick, high-speed steel this duty. fi and
n
232 slitting saws were used with 12 teeth per inch but without side relief or set to the teeth. As expected the thinner saw gave a cleaner cut and required less torque but as the blades are presented to the pipe at an angle of 45° excessive vibration and run out occurred as the saws became worn. Tungsten carbide and diamond tipped saws were both suggested as alternatives but not adopted because of their high cost and the comparatively short runs which the machine was called upon to execute.
Acknowledgements The author wishes to acknowledge the advice and help of C. H. Peek of British Geon Ltd who made pipe available for experiments with this machine and for the drainage trials and the
A MACHINE FOR SLITTING PLASTIC PIPE S
assistance of R. F. J. Rose who undertook the major part of the construction ofthe machine. REFERENCES
Someren, C. L. van. The use ofplastic drainage pipes in the Netherlands. Mimeo, Rep. Transl. from Cultuurtechniek, 1964, nos 1, 2, 3, Govt Servo Land and Water Use, Min. Agric. Fish., 1964 2 Ede, A. N. Innovations in land drainage methods. J. Proc. Instn Br. agric. Engrs, 1958, 14 (1) 8 3 Ede, A. N. New methods offield drainage. Agriculture, Lond., 1963,70 (2) 82 4 Boa, W. Development of a machine for laying plastic drains. J. agric. Engng Res., 1963, 8 (3) 221 5 Hawkins, J. C.; Marchant, W. T. B. Pipes. Br. Pat. Applic., 13250/63 6 Youngs, E. G. A comparison of the performance of some plastic and tile drains. J. agric. Engng Res., 1965, 10 (3) 202
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A Machine for Slitting Plastic Pipes VV.
T.B.~ARCHANT*
1. Introduction Rigid extruded p.v.c. drain tube in approximately 16 ft lengths has been used widely in Holland, mainly in conjunction with chain type trench excavating machines, with claimed overall economies of up to 20 %over clay pipe on handling and transport costs.' In this country Ede" has examined the feasibility of in-situ cast drains of porous concrete and Ede' and Boa" have used subsoiling tines to lay latch-up pipe made from p.v.c. foils. More recently this work has been extended, using similar laying equipment, to include the use of extruded p.v.c. tube made flexibleby corrugations . or slitting and thickwall polythene pipe. This note describes a laboratory machine for slitting extruded p.v.c, pipe" to render it both coilable and porous. It was able to process pipe of from 1·5 to 3·0 in dia, at pitches from 1·5 to over 6 in and its capacity when working at a pitch of 2·6 in was approximately 180 ft/h. A 300 ft length of a typical pipe (2,6 in o.d. with walls 0·04 in thick) slit with this machine forms into a coil 12 in wide on a mandrel of 48 in dia and with an outside diameter of 78 in, weighing 85 lb. The hydraulic performance of this pipe has been investigated by Youngs." It was found to be slightly better than that of wrapped 4 in clay tile drain, only half as good as that of a fully permeable drain tube, but nearly twice as good as the N.LA.E. latch-up p.v.c. foil liner. 4 It was found that slitting reduced the resistance of the pipe to compressive loads by less than 10 % but, as p.v.c. tends to be notch sensitive, the pipe was more likely to shatter. However, a total of 1600 ft of pipe have been successfully laid for evaluation purposes at VVrest Park and two other sites.
sides of the plane of the neutral axis of bending of the pipe, each slit extending to that plane at an angle 45° to the axis. The slits are made at a pitch of 1 pipe diameter and staggered by a t pitch between the two sides of the pipe. Although a commercial slitting machine would have to work in tandem with an extruder, moving along with the pipe in the manner of a flying cut-off saw, this machine is stationary and intermittently indexes the pipe past a pair of swinging circular saws. The pipe is supported horizontally in the working zone of the machine by two pairs of spring-loaded diabolo rollers (A) and is manipulated by two pairs of solenoid-operated clamps, one sliding (B) and the other stationary (C). Each 3t in dia slitting saw (D) is carried on an extension of a parallelogram linkage (E) so that it describes a curved path through the pipe about a centre remote from its cut. This ensures that the saws do not foul when the pipe is cut without stagger and also reduces the depth of engagement and hence the diameter of saw required. The two saw linkages are normally displaced axially relative to each other by a t pitch and are inclined to the pipe at equal and opposite angles of 45°: the saws swing in vertical planes perpendicular to each other. The movements of the saws and one clamp are derived from and synchronized by a combined two-lobed cam and two-throw crankshaft (F) with pins at 90°. The indexing mechanism consists of the sliding solenoid-operated clamp connected by a linkage (G) with a 1·5 to 6·0 in range of stroke adjustment to a cam follower (H) running on the periphery of the two-lobed cam. The cam profile is designed to give two lifts and falls of 3 in per revolution with short dwell periods at the transition points. The lift periods occupy 120° of cam movement followed by 10° of dwell and 40° of return movement and a further 10° dwell in each half revolution. The 2. Description of the machine The machine (Fig. 1) produces two sets of cam is made double-sided over the two return parallel slits perpendicular to and on opposite sections. Synchronization between movements of the saws and of the sliding clamp is obtained by • Cultivation Department, N.I.A.E. 230
231
W. T. B. MARCHANT
Fig. 1. The pipe slitting machine
making the 400 cam return movement coincide with the 200 of crank movement to each side of inner and outer dead centre positions, at which both saws arrive at the same instant. The length and geometry of the connecting rods are chosen to ensure that these saws are clear of the pipe over the 40° of crank movement, thus enabling the pipe to be indexed forward in readiness for cutting the next pair of slits. The solenoid clamps are opened and closed by a microswitch actuated by a second cam coaxial with the crank shaft and switching takes place during the appropriate 10° dwell period. Two independently switched electric motors are used: one (J) rated at t hp at 3000 rev/min drives the saws at a nominal cutting speed of 10 000 ft/min through flat belts and flexible shafts, the other (K) controls the traverse of the saws and drives the crankshaft at 7 rev/min through a small worm gear and double chain reduction. It was considered desirable that the saws should be running at full speed and clear of the pipe before the traverse was either started or stopped; this was achieved by operating a second microswitch from the solenoid switch cam which continues to feed current from the saw
motor circuit to the traverse motor until the saws are at either the inner or outer dead centre positions. In an emergency both switches (L) can be operated to stop the traverse and saws. The whole machine was normally covered by a hinged mesh guard fitted with an isolator switch (M) to cut out the saws in the event of the guard being lifted when they are running. 3.
Operation The slitting machine was used to prepare pipe for two trials undertaken for the Field Drainage Experimental Unit oftheM.A.F.F. and for a small area of clay land at Wrest Park. As it was never possible to set up the machine in line with an extruder, pipe was fed into the machine in lengths of 24 ft, thus time was spent joining successive lengths and the theoretical throughput of 180 ft/h was not achieved. As long as the pipe was reasonably straight the indexing mechanism worked satisfactorily, but where warped pipe was being cut, it was necessary for the operator to help the pipe through the machine. It is considered that further investigation would be needed to find the best type of saw for in thick, high-speed steel this duty. fi and
n
232 slitting saws were used with 12 teeth per inch but without side relief or set to the teeth. As expected the thinner saw gave a cleaner cut and required less torque but as the blades are presented to the pipe at an angle of 45° excessive vibration and run out occurred as the saws became worn. Tungsten carbide and diamond tipped saws were both suggested as alternatives but not adopted because of their high cost and the comparatively short runs which the machine was called upon to execute.
Acknowledgements The author wishes to acknowledge the advice and help of C. H. Peek of British Geon Ltd who made pipe available for experiments with this machine and for the drainage trials and the
A MACHINE FOR SLITTING PLASTIC PIPE S
assistance of R. F. J. Rose who undertook the major part of the construction ofthe machine. REFERENCES
Someren, C. L. van. The use ofplastic drainage pipes in the Netherlands. Mimeo, Rep. Transl. from Cultuurtechniek, 1964, nos 1, 2, 3, Govt Servo Land and Water Use, Min. Agric. Fish., 1964 2 Ede, A. N. Innovations in land drainage methods. J. Proc. Instn Br. agric. Engrs, 1958, 14 (1) 8 3 Ede, A. N. New methods offield drainage. Agriculture, Lond., 1963,70 (2) 82 4 Boa, W. Development of a machine for laying plastic drains. J. agric. Engng Res., 1963, 8 (3) 221 5 Hawkins, J. C.; Marchant, W. T. B. Pipes. Br. Pat. Applic., 13250/63 6 Youngs, E. G. A comparison of the performance of some plastic and tile drains. J. agric. Engng Res., 1965, 10 (3) 202
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