GB2196694A - I.C. engine valve gear - Google Patents

Description

GB2196694A 1 SPECIFICATION and releasing the first, second and third

rocker arms for relative angular movement. The cou Variable valve operation timing device in pling means has a piston slidably disposed in internal combustion engine guide holes defined in the rocker arms and 70 hydraulically operated to couple the rocker The present invention relates to valve operat- arms to each other.

ing mechanisms for use in internal combustion With the above structure, the guide holes of engines. More particularly, the invention re- the rocker arms are intended to be in registry lates to means for maintaining proper member with each other when the base-circle portions alignment in valve operating apparatus employ- 75 of the cams are slidably held against the 'cam ing plural cam force-transmitting members and slippers of the rocker arms, and the piston is coupling means for selectively connecting or operated in the aligned guide holes. If gaps disconnecting such transmitting members for (so-called, "tappet clearances- exist between independent operation or operation in unison the adjacent rocker arms and the valves, the in order to change the valve operation timing. 80 axes of the guide holes will not be properly Combustion chambers of four-cycle engines aligned, and thus will fail to allow smooth have intake and exhaust valves for supplying movement of the piston between the guide an air-fuel mixture into, and discharging a holes. To prevent such a problem, the device combustion gas from, the combustion cham- must be serviced or maintained frequently for bers according to engine operation cycles. 85 optimizing the tappet clearance at all times.

These valves are normally urged in a closing This, however, results in a complex and ex direction by valve springs disposed around the pensive process of keeping the parts at a de respective valve stems. The intake and ex- sired level of accuracy.

haust valves can be forcibly opened against One proposed solution to the above prob- the resiliency of the valve springs by cams 90 lem involves the provision of a hydraulic lash integrally formed on a camshaft that is driven adjuster for automatically adjusting the tappet by the crankshaft of the engine through a belt clearance. However, if a conventional lash. ad and pulley mechanism. juster is incorporated in a valve operation timThere have been proposed a variety of en- ing changing device of the type described gine arrangements in which each cylinder is 95 above at the end of a rocker arm which en provided with a plurality of intake or exhaust gages a valve stem, the rocker arm must be valves. When the engine operates at a low increased in size and consequently, have an speed, one of the intake or exhaust valves is increased inertial mass in order to avoid physi actuated, and when the engine operates at a cal interference with the timing changing de high speed, all of the intake or exhaust valves 100 vice.

are actuated. At the same time, the operation On the other hand, it is known to support a timing of the valves is varied according to the rocker arm pivotally with a lash adjuster hav rotational speed of the engine for increasing ing a ball joint on the projecting end of a the efficiency of charging the air-fuel mixture plunger. Although this arrangement is advan into the combustion chamber in a wide range 105 tageous in that the rocker arm can be reduced of engine operating conditions. in size, the point about which the rocker arm One such device for changing the valve op- is swingable varies in position, and the axes eration timing in. an internal combustion engine of the guide holes of the timing changing de is disclosed in Japanese Laid-Open Patent vice are brought out of mutual alignment since Publication No. 61-19911. Such device com- 110 each rocker arm is supported on the ball joint.

prises a camshaft rotatable about its own axis In view of the aforesaid shortcomings of the in synchronism with rotation of an engine; a prior art, it is a principal object of the present low-speed cam integrally formed on the cam- invention to provide a device for changing shaft in alignment with one of the intake or valve operation timing for an internal combus exhaust valves and having a cam profile corre- 115 tion engine, the device being arranged such sponding to low-speed operation of the en- that a hydraulic lash adjuster can be incorpor gine; a high-speed cam integrally formed on ated therein without impairing the operation the camshaft and having a cam profile corre- reliability of the device.

sponding to high-speed operation of the en- According to the present invention there is gine; a rocker shaft; a first rocker arm slidably 120 provided apparatus for altering valve operation held against the low-speed cam and engage- timing in an internal combustion engine having able with said one intake or exhaust valve; a a combustion chamber and a plurality of second rocker arm engageable with the other valves disposed in the intake or exhaust ports intake or exhaust valve; and a third rocker arm thereof, comprising:

slidably held against the high-speed cam; the 125 a plurality of cams rotatable in synchronism first through third rocker arms being mutually with said engine and each having a cam pro held in sliding contact and relatively angularly file adapted to impart a desired mode of oper movably supported on the rocker shaft; and ation to said valves; coupling means for selectively coupling the a plurality of transmission members operfirst, second and third rocker arms together 130 ated by the said cams for transmitting the 2 GB2196694A 2 movement of said cams to the said valves; through 6 there is shown a first embodiment coupling means for selective connection and of a valve operating mechanism for an internal disconnection of said transmission members, combustion engine based on the present in including guide holes and pistons extendable vention.

between adjacent guide holes; and 70 With reference to Figure 1, the body of the means for ensuring the lateral alignment of internal combustion engine (not shown) has a said guide holes, including means interposed pair of intake valves la, lb which can be between each said transmission member and opened and closed by a pair of low-speed its associated valve for biasing said transmis- cams 3a, 3b or by a single high-speed cam 4.

sion member against its associated cam. 75 The cams 3a, 3b, 4 are of eggshaped cross- Thus in a preferred form of the invention, section and integrally formed on a camshaft 2 when the engine operates in a high-speed that is rotatable in synchronism with rotation range, the transmission members are coupled of the engine at a speed ratio of 1/2 with to operate the valves by the high-speed cam. respect to the speed of rotation of the engine During low-speed operation of the engine, the 80 First through third rocker arms 5, 6, 7 swing transmission members are mutually disconable as transmission members in engagement nected to open the valves independently by with these cams 3a, 3b, 4 transmit to the the low-speed cam. The means for adjusting valves the operation determined by the pro gaps or tappet clearances in the transmission files of the cams. The internal combustion en members is separated from the means for 85 gine also has a pair of exhaust valves (not changing the valve operation timing, whereby shown) which can be opened and closed in the effects of displacement of the hydraulic the same manner as the intake valves l a, lb.

lash adjuster on the changing of the valve op- The first through third rocker arms 5, 6, 7 eration timing are avoided. are disposed adjacent to each other and are Some embodiments of the invention will 90 swingably supported on a rocker shaft 8 dis- now be described by way of example and posed above, and extending parallel to, the with reference to the accompanying drawings, camshaft 2. The first through third rocker in which: arms 5, 6, 7 have central portions pivotally Figure 1 is a plan view of a valve operating supported on the rocker shaft 8 and free ends mechanism having a valve operation timing 95 extending over the respective cams 3a, 3b, 4.

changing device according to the present in- The free ends of these first through third vention; rocker arms 5, 6, 7 have cam slippers 5a, 6a, Figure 2 is a sectional view taken along line 7a, respectively, on their lower surfaces which 11-11 of Figure 1; are held against the outer peripheral surfaces Figure 3 is a view, partly in section, taken 100 of the respective cams 3a, 3b, 4.

in the direction of arrow Ill in Figure 1; The first and third rocker arms 5, 7 are Figure 4 is an enlarged sectional elevational basically of the same configuration, and have view of a hydraulic lash adjuster; opposite free ends extending over the respec- Figure 5 is a sectional view taken along line tive intake valves la, lb.

V-V of Figure 3, illustrating operating parts of 105 Swing arms 9a, 9b are positioned between the device during lowspeed operation of the the respective intake valves la, lb and exten engine; sions of the rocker arms 5, 7. The swing Figure 6 is a view similar to Figure 5, illus arms 9a, 9b have ends swingably supported trating operating parts of the device during on ball joints 10a, 10b, respectively, and op high-speed operation of the engine; 110 posite free ends engaging the distal ends of Figure 7 is a sectional elevational view simi- the valve stems of the intake valves 'I a, lb.

iar to Figure 3, illustrating a second embodi- The rocker arms 5. 7 have free ends 5b, 7b ment of the present invention; abutting against upper surfaces of the respec- Figure 8 is a sectional elevational view simitive swing arms 9a, 9b.

lar to Figure 2, illustrating the second embodi- 115 The second rocker arm 6 is swingably sup- ment; ported on the rocker shaft 8 between the first Figure 9 is a sectional elevational view simi- and third rocker arms 5, 7. The second rocker lar to Figure 2, illustrating a third embodiment arm 6 extends from the rocker shaft 8 slightly of the present invention; toward a position intermediate the intake Figure 10 is a sectional view, taken along 120 valves la, lb. As illustrated in Figure 2, the line X-X of Figure 9, illustrating operating second rocker arm 6 has a cam slipper 6a on parts of the third embodiment during low- the lower surface of one end thereof, the cam speed operation of the engine; slipper Ba being slidably held against the high- Figure 11 is a view similar to Figure 10, speed cam 4. The lower surface of the oppo- illustrating operating parts of the third embodi- 125 site end 6b of the second rocker arm 6 is in ment during high-speed operation of the en- abutment against the upper end of a lifter 12 gine; and Figures 12 and 13 are fragmentary slidably fitted in a guide hole 11 a defined in a sectional elevational views illustrating other cylinder head 11. A coil spring 13 is disposed modifications of the present invention. under compression between an inner surface With particular reference to Figures 1. 130 of the lifter 12 and the bottom of the guide 3 GB2196694A 3 hole 11 a for normally urging the lifter 12 in an the high-pressure chamber 44 for normally bi upward direction thereby to keep the cam asing the plunger 42 to move upwardly. The slipper 6a of the second rocker arm 6 in slid- plunger 42 has an oil hole 49 defined in a ing contact with the high-speed cam 4 at all side wall thereof, and the casing 41 has an oil times. 70 hole 48 defined in a side wall thereof. The As indicated above, the camshaft 2 is rota- low-pressure chamber 43 is supplied with tably supported above the engine body, and working oil in the form of lubricating oil has the low-speed cams 3a, 3b aligned with through the oil holes 48, 49 and an oil hole the first and third rocker arms 5, 7, respec- 50 defined in the cylinder head 11. The ball tively, and the high-speed cam 4 aligned with 75 joint 10a (10b) is lubricated by oil from the the second rocker arm 6. As better shown in low-pressure chamber 43 through an oil hole Figure 3, each of the low-speed cams 3a 3b 51 defined in the top of the plunger 42.

has a relatively small cam lift and a profile As better shown in Figures 5 and 6, the corresponding to low-speed operation of the first rocker arm 5 has a first guide hole 17 engine. The outer peripheral surfaces of the 80 defined therein parallel to the rocker shaft 8 low-speed cams 3a, 3b are slidably held in and opening toward the second rocker arm 6.

contact with the cam slippers 5a, 7a of the The first rocker arm 5 also has a smaller first and third rocker arms 5, 7. The high- diameter hole 18 near the bottom wall of the speed cam 4 has a relatively large cam lift of first guide hole 17, with a step 19 being de a larger angular extent than that of the low- 85 fined between the smaller-diameter hole 18 speed cams 3a, 3b and a profile correspond- and the first guide hole 17. The second ing to high-speed operation of the engine. As rocker arm 6 has a second guide hole 20 described above, the outer peripheral surface defined between its opposite side surfaces in of the high-speed cam 4 is slidably held communication with the first guide hole 17.

against the cam slipper 6a of the second 90 The third rocker arm 7 has a third guide rocker arm 6. The lifter 12 is omitted from hole 21 communicating with the second guide illustration in Figure 3. hole 20. The third rocker arm 7 also has a The first through third rocker arms 5, 6, 7 smaller-diameter hole 23 near the bottom wall are selectively brought into a condition in of the third guide hole 21, with a step 22 which they are swingable together and 95 being defined between the smaller-diameter another condition in which they are displacea- hole 23 and the third guide hole 21. A still ble relatively to each other, by means of a smaller-diameter hole 24 is defined through coupling 14, hereinafter described, that is the bottom wall of the third guide hole 21 in mounted in holes defined centrally through the communication therewith.

rocker arms 5, 6, 7 and extending parallel to 100 In the first through third guide holes 17, 20, the rocker shaft 8. 21, there are mounted a first piston 25 mov- Retainers 15a, 151) are mounted on the up- able between a position in which the piston per ends of the valve stems of the intake interconnects the first and second rocker arms valves la, 1b. Valve springs 16a, 16b are 5, 6, and a position in which it releases them disposed around the respective valve stems 105 from each other, a second piston 26 movable between the retainers 15a, 15b and the en- between a position in which it interconects gine body for normally urging the intake the second and third rocker arms 6, 7 and a valves la, lb in a closing direction, Le, up- position in which it releases them from each wardly as viewed in Figure 3. other; a stopper 27 for limiting movement of The ball joints 10a, 10b, on which the re- 110 the first and second pistons 25, 26; and a spective swing arms 9a, 9b are swingably coil spring 28 for normally urging the first and supported, are part of hydraulic lash adjusters second pistons 25, 26 in a direction toward fixed to the cylinder head 11. As shown in their positions to release the first through third Figure 4, each of the hydraulic lash adjusters rocker arms 5, 6, 7 from each other.

40 is of a known construction including a bot- 115 The first piston 25 is disposed for sliding tomed cylindrical casing 41 and a plunger 42 movement between the first and second guide slidably fitted in the casing 41, the ball joint holes 17, 20, there being a hydraulic chamber 10a (10b) being on the upper end of the plun- 29 between the bottom of the first guide hole ger 42. The plunger 42 has a low-pressure 17 and the confronting end of the first piston chamber 43 defined therein. A high-pressure 120 25. The rocker shaft 8 has a supply passage chamber 44 is defined between the outer sur- 30 communicating with a hydraulic pressure face of the bottom wall of the plunger 42 and supply (not shown) for supplying working oil the inner surface of the casing 41. therefrom to the hydraulic chamber 29 through The plunger 42 has a hole 45 defined an oil passage 32 defined in the first rocker through the bottom wall thereof. The hole 45 125 arm 5. A hole 33 defined in the peripheral can be opened and closed dependent on the wall of the rocker shaft 8 connects the oil difference between pressures in the chambers passage 32 with the supply passage 30 irre 43, 44 by a ball-shaped check valve 46 dis- spective of how the first rocker arm 5 is an posed in the high-pressure chamber 44. A coil gularly moved.

spring 47 is disposed under compression in 130 The first piston 25 has an axial length such 4 GB2196694A 4 that, when one end thereof abuts against the delayed timing and their lift is increased ac step 19 in the first guide hole 17, the other cording to the cam profile of the high-speed end of the piston 25 does not project from cam 4.

the side of the first rocker arm 5 which faces If gaps, known as socalled, -tappet clear- the second rocker arm 6. The second piston 70 ances-, exist between the link members of 26 has an axial length equal to the entire the device, the pistons 25, 26 will not oper length of the second guide hole 20, and is ate smoothly. According to the present em slidably fittable in the second and third guide bodiment, therefore, hydraulic lash adjusters holes 20, 2 1. are added to the operation of the link mem- The stopper 27 includes a disk 27a on one 75 bers for automatically adjusting the tappet end thereof which is slidably fitted in the third clearances.

guide hole 21 and a guide rod 27b on the As illustrated in Figure 3, while the cam other end which is inserted through the hole slippers 5a, 6a, 7a are engaging the base 24. A coil spring 28 is disposed around the circle portions C of the cams, no external guide rod 27b between the disk 27a and the 80 force is applied to the plungers 42 of the lash bottom of the smaller-dia meter hole 23. adjusters (Figure 4), and hence the plungers Operation of the above described device is 42 are urged upwardly only under the resili- as follows. Referring to Figure 5, when the ency of the coil springs 47. There are thus engine operates in a low- or medium-speed developed no gaps between the free ends of range, a control valve (not shown) is closed 85 the swing arms 9a, 9b and the upper ends of so that no hydraulic pressure is supplied to the valve stems. Nor do gaps occur between the hydraulic chamber 29. Therefore, the pis- the ends 5b, 7b of the rocker arms 5, 7 and tons 25, 26 are positioned respectively in the the upper surfaces of the swing arms 9a, 9b, guide holes 17, 20, as shown in Figure 5, or between the low-speed cams 3a, 3b and under the bias of the coil spring 28, whereu- 90 the cam slippers 5a, 7a.

pon the rocker arms 5, 6, 7 are relatively As the cams 3a, 3b start pushing the angularly movable. With the coupling 14 being rocker arms 5, 7, the intake valves la, 1b thus in the disconnect position, upon rotation and the plungers 42 are subjected to forces of the camshaft 2, the first and third rocker tending to move them downwardly. At the arms 5, 7 are swung by sliding contact with 95 same time the pressure in the high-pressure the respective low-speed cams 3a, 3b. The chamber 44 of the lifter is increased as the intake valves la, 1b are therefore opened at a hole 45 is closed by the check valve 46. The delayed timing and closed at an advanced tim- vertical position of the ball joints 10a, 10b ing, with their lift being small. At this time, supporting the respective swing arms 9a, 9b the second rocker arm 6 is swung by sliding 100 is therefore fixed, allowing the intake valves contact with the high-speed cam 4, but the la, 1b to start their lifting stroke while elimi swinging movement thereof does not affect nating the gaps between the various engaging the opertaion of the intake valves 'I a, l b at surfaces.

all. When the cam slippers 5a, 7a slidingly con- During high-speed operation of the engine, 105 tact the basecircle portions C again upon fur- the control valve is opened to introduce hy- ther rotation of the camshaft 2, the intake draulic pressure into the hydraulic chamber 29 valves la, 1b are closed, and the pressure on through the supply passage 30, the hole 33, the plungers 42 is reduced. The check valve and the oil passage 32. As shown in Figure 46 opens the hole 45, and the swing arms 6, the first piston 25 is moved into the sec- 110 9a, 9b are lifted only under the bias of the ond rocker arm 6 under the hydraulic pressure coil spring 47. Any lubricating oil leakage from against the bias of the coil spring 28, and the the oil hole 51 and between the casing 41 second piston 26 is pushed by the first piston and the plunger 42 is compensated for by oil into the third rocker arm 7. The first and supplied via the oil holes 48, 49, 50.

second pistons 25, 26 are moved together 115 Figures 7 and 8 show a second embodi- until the disk 27a of the stopper 27 abuts ment of the present invention. Those parts against the step 22. Now, the first and sec- which are identical to those of the first em ond rocker arms 5, 6 are interconnected by bodiment are denoted by identical reference the first piston 25, and the second and third numerals and will not be described in detail.

rocker arms 6, 7 are interconnected by the 120 In the first embodiment, the rocker arms 5, second piston 26. 6, 7 are centrally pivoted, and the rocker When the first through third rocker arms 5, shaft 8 is disposed above the camshaft 2.

6, 7 are thus interconnected by the coupling According to the second embodiment, how- 14, the second rocker arm 6, in sliding con- ever, the rocker arms 5, 6, 7 are pivoted at tact with the high-speed cam 4, which is 125 an end, and the rocker shaft 8 is disposed swung to the greatest angular extent, causes below the camshaft 2. As with the first em the first and third rocker arms 5, 7 to swing bodiment, the upper surfaces of the swing in unison with the second rocker arm 5. arms 9a, 9b supported by the respective hy Therefore, the intake valves la, 1b are draulic lash adjusters 40 are depressed by the opened at an advanced timing and closed at a 130 lower surfaces 5c, 7c of the free ends of the GB2196694A 5 first and second rocker arms 5, 7 for opening intake valves 1 a, 1 b and the swing arms 9a, the intake valves 1 a, 1 b. 9b are interconnected by push rods 66, The The structures of the coupling 14 and the lash adjusters 40 are mounted in the rocker lash adjusters 40 remain the same as those of arms 5, 7 in engagement with the valve the first embodiment, and the lifter 12 for 70 stems of the intake valves 1 a, 1 b. The bucket pressing the second rocker arm 6 against the lifters 61, 62, 63 shown in Figures 9 through high-speed cam 4 is structurally identical to 11 may be employed in coaction with the sw that of the first embodiment. ing arms 9a, 9b. The lash adjusters 40 may Figures 9 through 11 show a third embodi- be positioned on the rocker arms 5, 7 adja- ment of the present invention in which the 75 cent to the push rods 66.

rocker arms 5, 7 of the second embodiment With the present invention as described are replaced with piston-type bucket lifters 61, above, a hydraulic lash adjuster can approlark 62, 63 disposed between the cams 3a, 3b ately be incorporated in a device for changing and the swing arms 9a, 9b. The lifter 62 valve operation timing so that tappet clearance which engages the central high-speed cam 4 80 in a valve operating mechanism having such a is spring-biased as by the lifter 12 of the pre- timing changing device can be kept at a de vious embodiments. sired level at all times. Therefore, operational The bucket lifters 61, 62, 63 are sliclably reliability of the timing changing device can be fitted in guide holes 64 defined in a cylinder increased, and the valve operating mechanism head 11. The bucket lifters 61, 62, 63 have 85 is made free of maintenance.

first through third guide holes 17, 20, 21, Although certain preferred embodiments of respectively, defined therein and extending in the invention have been shown and described, a direction normal to the axes of the lifters it should be understood that various changes 61, 62, 63 along which they are slidable. The can be made therein without departing from pistons and stopper of a coupling 14, which 90 the scope of the appended claims. For is similar to the coupling 14 of the first and example, the pistons of the coupling may be second embodiments, are slidably fitted in the actuated electrically or mechanically rather first through third guide holes 17, 20, 21. Flat than hydraulically; the link or transmission surfaces which slidably contact each other are members of the device may be used in vari formed between adjacent ones of the bucket 95 ous combinations; and the lash adjusters. may lifters. The bucket lifters 61, 62, 63 are cir- be positioned in various locations. Also, while, curnferentially positioned by these flat contact- in the above embodiments, the two valves are ing surfaces. simultaneously changed in their operation tim- Operation of the device according to the ing by the three separate rocker arms (or third embodiment is essentially the same as 100 bucket lifters), the present invention is also that of the first and second embodiments. applicable to a valve timing changing device When no working oil is supplied from an oil for disabling one of the valves in a certain passage 30 to the coupling 14, the bucket engine speed range by using two separate lifters 61, 62, 63 are independently slidably rocker arms (or bucket lifters).

movable as shown in Figure 10. When work- 105 It is to be clearly understood that there are ing oil is supplied, the pistons and stopper of no particular features of the foregoing specifi the coupling 14 are moved to cause- the lifters cation or of any claims appended hereto, 61, 62, 63 to move in unison with each which are at present regarded as being essen other. tial to the performance of the present inven- Figure 12 shows a modification of the sec- 110 tion, and that any one or more of such feaond embodiment illustrated in Figure 7. The tures or combinations thereof may therefore swing arms 9a, 9b are replaced with piston- be included in, added to, omitted from or de type bucket lifters 65a, 65b which are analoleted from any of such claims if and when gous to those of the third embodiment shown amended during the prosecution of this appli in Figures 9 through 11, for opening the in- 115 cation or in the filing or prosecution of any take valves 1 a, 1b. The coupling 14 is posi- divisional application based thereon.

tioned on a side of the rocker shaft 8 remote

Claims (5)

1. from the intake valves 1 a, 1b, but may be CLAIMS located in the same

   position as with the sec- 1. Apparatus for altering valve operation ond embodiment (Figure 7). 120 timing in an internal combustion engine having In this modification, the lash adjusters 40 a combustion chamber and a plurality of are disposed in the respective lifters 65a, valves disposed in the intake or exhaust ports 65b. The swing arms 9a, 9b of the first emthereof, comprising:

   bodiment shown in Figure 3 may be replaced a plurality of cams rotatable in synchronism with the bucket lifters 65a, 65b of this modifi- 125 with said engine and each having a cam pro cation. file adapted to impart a desired mode of oper- Figure 13 shows another modification in ation to said valves; which the coupling 14 is incorporated in the a plurality of transmission members oper- swing arms 9a, 9b actuated by the camshaft ated by the said cams for transmitting the 2, and the rocker arms 5, 7 for operating the 130 movement of said cams to the said valves; 6 GB2196694A 6 coupling means for selective connection and disconnection of said transmission members, including guide holes and pistons extendable between adjacent guide holes; and means for ensuring the lateral alignment of said guide holes, including means interposed between each said transmission member and its associated valve for biasing said transmis sion member against its associated cam.
2. 2. Apparatus according to claim 1 in which said biasing means comprises a hydraulic lash adjuster having a movable piston for biasing said transmission member against said cam.
3. 3. Apparatus according to claim 2 including an elongate swing arm positioned between said transmission member and said valve, said swing arm having one end engaging said valve, its other end engaging said lash ad juster, and a follower surface intermediate said ends for engaging said transmission member.
4. 4. Apparatus according to claim 3 in which said transmission members comprise rocker arms mounted for pivotal movement in side by-side relation on a rocker shaft.
5. 5. Apparatus according to claim 3 in which said transmission members comprise laterally adjacent axially movable bucket lifters inter posed between said cams and said valves.

   Published 1988 at The Patent Office, State House, 66/71 High Ho I born, London WC I R 4TP Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD.

   Printed by Burgess & Son (Abingdon) Ltd Con. 1/87