GB2188577A - Shearing machine - Google Patents

Abstract

A shearing machine (1) comprises a frame, a work-table (13) fixed to the frame, a lower blade (15) detachably mounted on the work-table (13), a vertically movable ram (19) for holding an upper blade (17), upper and lower rear guide means (27, 29) for the ram (19), front guide means (37) for the ram (19), and drive means (55) for the ram (19), the drive means (55) being connected to the rear of the ram (19) at a point above the lower rear guide means (29). The location of this point of connection and the provision of a spring (49) bearing on guide means (37) maintain engagement between the ram and the guide means. Variable fluid pressure hold down means (103) and an adjustable back gauge (77) are provided and the work may rest on a vertically movable and/or tiltable fluid-biassed supports (149). <IMAGE>

Description

SPECIFICATION Shearing machine This invention relates to a shearing machine having apairofupperand lower shearing bladesforcutting or shearing sheet-like materials such as sheet metals.

Asiswell known,ashearing machineforshearing sheet-like materials such as sheet metals comprises a pair of opposed upright plates, a pair elongate upper and lower shearing blades and a work-table on which a workpiece is fed and held to be sheared. The lower blade is horizontally fixed to the work-table and the upper blade is held by a ram which is arranged to move up and down between the upright plates to move the upper blade towards and away from the lower blade. Also, a plurality of hydraulic or pneumatic cylinder means are provided atthefront ofthe shearing machine to hold theworkpieceto be sheared down on the work-table. Furthermore, a back gauge is provided to set the widths or lengths into which the workpiece is to be sheared.

A disadvantage of conventional shearing machinesisthatthe hydraulicorpneumaticmeans for holding down the workpiece to be sheared virtually strike the workpiece onto the work-table, because a high pressure is suddenly produced in the hydraulic or pneumatic cylinder. Therefore, a lot of noise is produced and theworkpiece may be damaged.

Another disadvantage of conventional shearing machines is thatthe workpieces, which are long and wide, tend to bend and curl into desirable shapes, because they cannot be perfectly held when being sheared.

Afurther disadvantage of conventional shearing machinesisthatthe back gauge means are in the way when a workpiece is to be sheared into an irregular size without using the back gauge means while otherworkpieces are being continuously sheared into a certain size.

It is an object of the present invention to enable the provision of a machine wherebythe above disadvantages may be overcome or at least mitigated.

The invention enables the provision of a shearing machine in which the ram can be accurately and smoothly moved up and down using a simple arrangement without the need fortroublesome adjustment. In one aspect of the invention, therefore, a shearing machine is arranged so that the ram, when vertically moved, is resiliently guided by spring means and is driven by driving means in such a manner as to be kept urged into contact with the guide means.

The invention further enables the provision of a shearing machine having means which can firmly hold the workpiece being sheared without producing a noise and damaging the workpiece. To attain this object, a hydraulic pump meansforthe hold-down means is provided with a large diameter piston which can supply a large amount of flow under low pressure and damp the surge and a small diameter piston which can supply a small amount offlow under high pressure.

The invention still further enables the provision of a shearing machine which can perform shearing operations to produce fine workpieces without bending and curling. Forthis purpose,theshearing machine is provided with means for holding up the workpiece being sheared to prevent the workpiece from bending and curling.

The invention also enables the provision of a shearing machine with a back gauge which can be used to set the widths or lengths into which the workpiece is to be sheared but can be moved out of the way to enable a workpiece to be sheared into a different size.

For a better understanding of the present invention, and to show how the same may be put into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 7 is a front elevational view of a shearing machine in accordance with the present invention, Figure2is a sectional view taken along the line Il-Il of Figure 1, Figure3isadiagrammaticviewofa hydraulic circuit ofthe shearing machine of Figures 1 and 2, Figure 4 is an enlarged sectional viewtaken along the line IV-IV of Figure 2 with portions omitted, Figure5is a sectional view taken along the lineV-V of Figure 4, and Figure 6 is a diagrammatic view of a different hydraulic circuit.

Referring to Figures 1 and 2, a shearing machine I comprisesa pair of upright plates 3, 5, an upperfront plate 7, a lowerfront plate 9 and a beam member 11.

The upright plates 3 and 5 are vertically disposed in parallel with each other and are integrally connected with each other by the upper and lowerfront plates 7 and 9 and the beam member 11. The upper and lower front plates7 and 9 are vertically fixed totheupper and lower front portions, respectively, of the upright plates 3 and 5, and the beam member 11 is horizontallyfixed between the rearward top portions of the upright plates 3 and 5. Also, the shearing machine 1 is provided with a work-table 13 which is horizontally fixed to the top end of the lowerfront plates 9 in such a manner as to frontward project so that a work-sheet Wto be sheared can be fed thereon.

As shown also in Figures 1 and 2, an elongate lower blade 15 is detachably fixed horizontallyto the back edge of the work-table 13 on the top of the lower front plate 9, and also an elongate upper blade 17 is detachablyfixedto a ram 19 which is vertically movable between the upright plates 3 and 5. As is conventional, the upper and lower blades 17 and 15 are so arranged as to cooperate with each otherto shearthework-sheetWwhen the ram 1 9 is lowered to lower the upper blade 17. Particularly, the ram 19 is a square plate-like memberwhich is formed at its lower end with an elongate slope, and the upper blade 17 fixed aslantto such a slope to provide a rake angle.Also, the ram 19 is provided at its rear edges with a pair of vertical ribs 21 which symmetrically project rearward and also project downward from the lower end ofthe ram 19 belowthe level ofthetop surface ofthework-table 13.

As shown in Figure 2, in orderto guidethevertical movementofthe ram 19, a pairofupperguide plates 23 and a pair of lower guide plates 25 are fixed to the ribs 21 ofthe ram 19, and a pairofupperguide rollers 27 and a pair of lower guide rollers 29 are provided on shafts 31 and 33, respectively. The upper and lower guide plates 23 and 25 are vertically fixed to the upper and lower ends, respectively, ofthe ribs 21 ofthe ram 19 in such a manner as to extend longer than the stroke length of the ram 19. The upper and lower guide rollers 27 and 29 freely rotatably disposed on the shafts 31 and 33 in a manner such thattheywill be always kept in rolling contactwith the upper and lower guide plates 23 and 25, respectively, when the ram 19 is vertically moved.

The shafts 31 and 33 ofthe guide rollers 27 and 29 are horizontally held on the upper and lower portions, respectively, of the upright plates 3 and Sin vertical alignmentwith each otherto keep always the upper an lower guide rollers 27 and 29 in contact with the upperand lowerguideplates23and25.Also,the shafts 33 forthe lower guide rollers 29 are so provided thatthe lower guide rollers 29 will be in rolling contact with the lower guide plates 25 at a level which is lower than the level of the top surface ofthework-table 13 as designated by C.

In orderto keep the upper and lower guide plates 23 and 25 in contactwith the upper and lower guide rollers 27 and 29, a pai r of fro nt g u ide plates 35 a re vertically fixed to the frontsurface of the ram 19, and a pair offront guide rollers 37 are provided on the upper front plate 7 in rolling contact with the front guide plates 35. Each ofthefront guide rollers 37 is freely rotatably held by means of a shaft 39 on a holding means 41 which is horizontally movably disposed in a bore formed through the upper front plate 7. The outer end of the holding means 41 projecting frontward from the upper front plate 7 is horizontally movably disposed in a casing 43 which is secured to the upperfront plate 7 and is covered by a box nut 45.Also, in orderto keep the respective front guide rollers 37 in contact with the respective front guide plates 35, an adjusting bolt 47 is horizontally disposed on the box nut 45 to extend horizontally toward the holding means 41, and a spring 49 is disposed around the bolt 47 to bias the holding member41 rearwardly. Thus, the front guide rollers 37 are biased bythe respective spring 49 into rolling contactwith the front guide plates 35 to bias the ram 19 to keep the upper and lower guide rollers 27 and 29 in rolling contactwith the upper and lower guide plates 23 and 25 so thatthe ram 19 can be accurately moved up and down without shaking.In this connection, it will be understood that only a single set of the front guide rollers 37 and the front guide plates 35 can be emplpyed, although two sets of them have been described as employed in the preferred embodiment.

Referring again to Figure 1, in orderto preventthe ram 19 from shaking laterally rightward and leftward when vertically moving, a pair of side guide plates 51 are vertically fixed to the both sides ofthe ram 19, and a pair of side guide rollers 53 are provided on the upright plates 3 and Sin rolling contact with the side guide plates 51. The side guide plates 51 are disposed in the same manner as the front guide rollers 37 to cooperate with the side guide plates 51 to hold and stop the ram 19 from shaking.

In the above described arrangement, the ram 19 will be held and stopped from shaking bythe upper and lower guide rollers 27 and 29, the front guide rollers 37 and the side guide rollers 53 when it is moving verticallyto bring the upper blade 17 toward and away from the lower blade 15. Also, the guide rollers 27,29,37 and 53 are kept resiliently in rolling contact with the guide plates 23,25,35 and 51 of the ram 19 by the springs 49, and therefore there is no problem about the guide clearance ofthe ram 11. In this connection, however, it will be understood that some antifriction members can be employed instead ofthe guide rollers 27,29,37 and 53 to cooperate with the guide plates 23,25,35 and 51.

Referring furtherto Figures 1 and 2, in orderto move the ram 19 up and down, a driving shaft 55 is horizontally disposed beneath the ram 19 between the upright plates 3 and 5. As a matter of importance, the driving shaft 55 is located beneath the ram 19 but a little much rearward than the vertical plane where the ram 19 is vertically moved. The driving shaft 55 id held bythe upright plates 3 and 5 by means of bearing means 57, and it is connected to a driving motor 59 in a conventional mannertodrivetheram 19. The driving shaft 55 is provided at its opposite ends with a pair of eccentrics 61 each fixed thereto by a key 63, and the eccentrics 61 are connected by respective connecting rods 65 to the ribs 21 of the ram 19 by means of respective pins 67.More importantly, the pins 67 of the connecting rods 65 are located at a lower level than the level ofthetop surface of the work-table 13 but at a higher level than the point Cwherethe lowerguide rollers 29 will be in rolling contactwith the lower guide plates 25. More particularly, the connecting rods 65 are pivotally connected to the eccentrics 61 and are pivotally connected to the ribs 21 of the ram 19 by the pins which are in horizontal alignment with each other.

Thus, when the driving shaft 55 is driven by the driving motor 59, the eccentrics 61 will move the ram 19 up and down by means of the connecting rods 65 and the pins 67.

In the above described arrangement, a vertical component VEand a horizontal componentllwill act on the pins 67 of the connecting rods 65 when the ram 19 is lowered by the driving shaft 55 and the eccentrics 61. Thus, the ram 19 will have a tendency to be tilted clockwise in Figure 2 by the moment of the horizontal componentHaboutthe point Cwhere the lower g u ide rol lers 29 wi li be in rolling contact with the lower guide plates 25, since the pins 67 are located higherthan the point C. Also, the upper blade 17 will be subject to a vertical upward shearing resistance or reaction and a horizontal rearward componentwhen shearing the work-sheetW in cooperation with the lower blade 15. Accordingly, the ram 19, when lowered by the driving shaft 55 and the eccentrics 61,will be urged rearward to press the upper and lower guide plates 23 and 25to the upper and lower guide rollers 27 and 29 to lower without shaking to bring down the upper blade 17.

As shown also in Figure 2, a balancing means 69, which is shown as an air cylinder in the preferred embodiment, it provided to biasthe ram 19 in the upper rearward direction in order to enable the ram 19 to smoothly raised. Particularly, the balancing means 69 is pivotally connected at its upper end by a pin 71 to the beam member 11 by means of a bracket 73, and it is also connected at its lower end to a bracket 75 fixed to the ram 19. Thus, the ram 19 can be not only smoothly raised but also accurately raised and lowered with the upper and lower guide plates 23 and 25 kept in contact with the upper and lower guide rollers 27 and 29.

As shown in Figure 2, in order to set the widths or lengths into which the work-sheet W is to be sheared, an elongate back gauge 77 is horizontally provided at the back of the upper and lower blades 17 and 15 in parallel therewith so asto stopthe work-sheetWwhich is fed overthe lower blade 15.

The back gauge 77 is carried by a pluraiity of carriers 79 each having rollers 81 so that it may be moved horizontally toward and away from the lower blade 15. The carriers 79 are movably mounted, by means ofthe rollers81, on rails83which are disposed on elongate supporting members 85 at right angles to the upper blade 17. The supporting members 85 are mounted in parallel with each other on the underside of a plate-like base member 87 which is horizontally fixed to the lower rearend ofthe ram 19 at right angles thereto in a cantilever manner. In orderto move the carriers 79 on the rails 83, lead screws 89 having nut members 91 are rotatably provided on the supporting members 85 and are connected to the carriers 79 by means of the nut members 91.The carriers 79 are pivotally connected to the nut members91 by means of pins 93 ina mannersuch that it can be swung upward about the pins 93 away from the level where the work-sheet W to be sheared is horizontally moved. Also, cams 95 are provided on the rails 83 in the proximity of the rear ends thereof so that the rollers 81 will ride thereon to enable the ca rriers 79 to be swung u pward about the pins 97.

More particularly, the cams 95 are so arranged asto befitted in a number of bores on the rails 83 so that they can be removably placed onto any place on the rails 83 at discretion. The lead screws 89 are connected with each other by means of gear boxes and a shaft 99 to be simultaneously driven bya motor 101 to move the carriers 79 by means ofthe nut members 91.

In the above described arrangement, the back gauge 77 will be horizontally moved toward and away from the lower blade 15 with the carriers 79 by the lead screws 89 and the nut members 91 to set the widths or lengths into which the work-sheet W isto be sheared. Also, when the rollers 81 ofthe carriers 79 are brought onto the cams 95 on the rails 83, the carriers 79 will be upwardly swung aboutthe pins 93 to bring the back gauge 77 out of the way from the level where the work-sheet W is horizontally moved.

Thus, the back gauge 77 can be brought up by moving the carriers 79 onto the cams 95 from the rails 83 so tahtthe work-sheet W can be moved further rearward to be sheared into a wider or longer workpiece. Also, itwill be understood thatthe cams 95 can be adjustably moved to any place on the rails 83 so as to enable the back gauge 77 to be raised out of the way at any desired positions on the rails 83.

Referring to Figure 3 in addition to Figures 1 and 2, a plurality of hold-down means 103 are mounted on the lower portion of the upper front plate 7 in a rowto hold the work-sheet Wto be sheared on the work-table 13. Each of the hold-down means 103 comprises a hydraulic cylinder 105, a piston and rod 107 which is vertically slidably disposed in the cylinder 105 and is provided at its lower end with a hold-down member 109, a spring 111 which is disposed in the cylinder 105 to bias the piston and rod 107 upwardly. The arrangement is such that the piston and rod 107 is downwardly urged by the hydraulicfluidagainstthespring 111 to enable the hold-down means 103 to hold downthework-sheet Wto be sheared onto the work-table 13.

The hold-down means 103 are hydraulically connected bya pipe 1 13 to a pump means 115which is driven by a cam 117 which iscoaxiallyfixedtothe driving shaft 55 forthe ram 19 by a key 119 so as to rotate therewith, The pump means 115 is constructed of a casing 121 which is formed with a large diameter bore 123, a small diameter bore 125 connected to the large diameter bore 123 and a passage 127 connecting the small diameter bore 125 and the pipe 113.More particulary,the large diameter bore 123 is formed to be outwardly open, the small diameter bore 125 is formed in connection with the innermostend ofthe largerdiameter bore 123 in axial alignment therewith and the passage 127 is formed to connect the innermost end of the small diameter bore 125 to the pipe 113.

In the casing 121 ofthe pump means 115, a cup-like piston 129 is slidably disposed in the large diameter bore 123, and a plunger 131 having a stem 133 is slidably mounted on the piston 129 so that it may be inserted into the small diameter bore 125.

Particuiarly, the plunger 131 itself is disposed on the inner side of the piston 129, and the stem 133 is slidably inserted in a bore formed through the center ofthe piston 129 in a manner such thatthe stem 133 is outwardly projected from the piston 129. The stem 133 of the plunger 131 is provided at its outer end with a block 135 on which a cam follower 137 is rotatably disposed in rolling contact with the cam 117 on the driving shaft 55 forthe ram 19.Also, a spring 139 is disposed in the large diameter bore 123 to bias the piston 129 outwardly, and another spring 141 which is stronger than the spring 139 is biased onthestem l33oftheplungerl3l betweenthe piston 129 and the block 135to urge the cam follower 137 into rolling contact with the cam 117.

The arrangement is such thatthe piston 129 is kept stopped from jumping out of the large diameter bore 123 bythe cam 117 by means of the cam follower 137, the block 135 and the spring 141 and the cam followerl37will inwardlypushtheblockl35,the stem 133 and the plunger 131 when the cam 117 is rotated bythe driving shaft 55. Thus, when the cam 117 is rotated, the cam follower 137 will initially move the piston 129 inwardly againstthe spring 139 by means of the block 135 and the spring 141 which is strongerthan the spring 139 until the piston 129 reaches its innermost limit.Then, afterthe piston 129 has reached the innermost limit, the cam follower 137 will move the plunger 131 inwardly into engagement with the small diameter bore 125 againstthespring 141 as the cam 117 isfurther rotated. In this connection, the cam 117 is so arrangedthatitwill cause the cam follower 137 to bring the plunger 131 to its innermost limit inthe small diameter bore 125 just before the ram 19 is lowered by the driving shaft 55 to enable the upper blade 17 to shear the work-sheetW in cooperation with the lower blade 15.Also, of course the hydraulic fluid is supplied to prevailthroughoutthelarge diameter bore 123, the small diameter bore 125,the passage 127,the pipe 113 and allthehold-down means 103.

As shown also in Figure 3, a reservoir 143 in which the hydraulic fluid is contained is connected to the pipe 113 by means of a relief valve 145 and a check valve 147. Thus, the hydraulic fluid can be drained from the pipe 113 into the reservoir 143throughthe reliefvalve 145 and also can be supplied into the pipe 113from the reservoir 143throughthe checkvalve 147.

In the above described arrangement, each ofthe piston and rods 107 ofthe hold-down means 103will be initially moved downwardly by a large amount of hydraulic fluid under low pressure from the pump means 1 1 5 when the piston 129 ofthe pump means 115 is inwardly moved in the large diameter bore 123. Accordingly, when the piston 129 is inwardly moved, the hold-down members 109 of the hold-down means 103 will lightly hold down the work-sheetWto be sheared onto the work-table 13 under low pressure with reduced noises and without hurting the work-sheet W. Also,the spring 141 of the pump means 1 15will dampthe surgewhichwill occur in the hydraulic circuit when the hold-down members 109 are brought into contact with the work-sheet Wto hold down it onto the work-table 13.

Afterthe piston 129 has reached its innermost limit in the large diameter bore 123 ofthe pump means 1 15, the plunger 131 willbemovedinthesmall diameter bore 125, and the piston and rods 107 will befurtherurgeddownwardlybyasmall amountof hydraulicfluid under high pressure.Thus,the work-sheetW, which has been lightly held down onto the work-table 13 under low pressure, will be finallyfirmlyheld down bythe hold-down members 109 under high pressure bythe action of the plunger 131 without noise and also without being hurt by the hold-down members 109. Also, when the work-sheet W is being held down onto the work-table 13 bythe hold-down members 109, the surplus hydraulicfluid will be drained into the reservoir through the relief valve 145.After the work-sheet W has been firmly held down by the hold-down members 109, the ram 19 will be lowered by the driving shaft 55to enable the upper blade 17 to shear the work-sheetW in cooperation with the lower blade 15. Afterthe work-sheetW has been sheared bythe upper and lower blades 17 and 15, the driving shaft 55 will raise the ram 19and rotatefurtherthe cam 1 17to enable the cam follower 137 and the springs 141 and 139 to move the plunger 131 and the piston 129 outwardly.

Afterthework-sheetW has been sheared, the piston and rod 107 and the hold-down members 109 will be raised by the springs 111 to release the work-sheetW as the piston 129 and the plunger 131 are moved outwardly by the springs 139 and 141. Also, some amountofthe hydraulic fluid will sucked into the pipe 1 13 from the reservoir 143 bythe piston 129 and the plunger 131 which are moved outwardly by the springs 139 and 141. It isto be noted that pneumatic pump means can be employed instead ofthe hydraulic pump means 115 to embody the principles of the present invention.Referring to Figures 2,4 and 5,atrain of hold-up members 149, each being an elongate square block, are provided just benath the upper blade 17 atthe back of the lower blade 15 in parallel therewith to upwardly hold up the work-sheetW to the upper blade 17 when the work-sheetW is being sheared by the upper and lower blades 17 and 15. The hold-up members 149 are so arranged as to hold up the work-sheetW being sheared in a manner such that the work-sheetW is held or gripped between the hold-up members 149 and the upper blade 17 as the upper blade 17 is lowered. Therefore, the hold-up members 149 are so arranged asto be moved up and down and also be tilted to comply with the motion of the upper blade 17 which is detachably fixed to the lower end ofthe ram 19 atan inclination or angle to the lower blade 15 to have a rake angle.

As shown in Figure 4, each of the hold-up members 149 is formed at one of its ends with a horizontal cylindrical bore 149which is partially notched into a more or less semi-cylindrical shape, and they are connected with each other by a joint block 151 fitting in the bore 149b by means of a bolt 153. More particularly, the hold-up members 149 are spaced from each other by a slight length, and the joint block 151 is fittingly engaged in the cylindrical bore 149b so that each ofthehold-up members 149 can be swung aboutthejointblockl5l.Thus,the hold-up members 149 are connected with each other so that each of them can betilted independently of the other to comply with the motion of the upper blade 17.

Each ofthe hold-up members 149 is fixed by a plurality of bolts 155 to one of carrier members 157, each of which is formed at its central portion with a C-shaped opening 1 57o facing or opening downwardly. The carrier members 157 are disposed at the back ofthe lower front plate 9 is slidable contact therewith so that it may be moved up and down and tilted rightward and leftwardtogetherwith the hold-up members 149. In orderto guide the movement ofthe carrier members 157, an elongate guide plate 159 is horizontally fixed to the backofthe lowerfront plate 9 by a plurality of bolts 161 by means of a plurality of spacer blocks 163 each of which is located between the carrier members 157.

Also, one of the carrier members 157 is pivotally connected to the back of the lower front plate 9 by a link 165 which is pivoted at one of its ends to a portion of one of the carrier members 157 by a pin 167 and is pivoted at the other end on a pin 169 which is spanned between the guide plate 159 and the back of the lower front plate 9. Thus, the carrier members 157 can be moved up and down and be tilted rightward and leftward between the guide plate 159 and the back ofthe lowerfront plate 9 and also between the spacer blocks 163 to enable the respective hold-up members 149 to comply with the movementofthe upper blade 17.

In orderto move the hold-up member 149 up and down, a plurality of hydraulic motors 171 each having a piston rod 173 are provided beneath the carrier members 157, and their piston rods 173 are pivotally connected to the carrier members 157 by pins 175. The hydraulic motors 171 are substantially vertically disposed with their piston rods 173 upwardly projected into connection with the carrier members 157, and they are pivotally mounted onto the back of the lowerfront plate 9 by means of pins 177 in such a manner as to be swung slightly rightward and leftward. Thus, the hold-up members 149 are held and moved up and down and also tilted rightward and leftward bythe hydraulic motors 171 by means of the carrier members 1 to hold up the work-sheet W being sheared in compliance with the movement of the upper blade 17.In this connection, the hydraulic motors 171 are so arranged as to hold the hold-up members 149 on a level with the lower blade 1 5 so that the work-sheetWto be sheared may be horizontally placed on the lower blade 15 and the hold-up members 149, when the piston rods 173 are fully extended to their uppermost limits by the hydraulicfluid.

Referring to Figure6,the hydraulic motors 171 are connected bya pipe 179to a control valve 181 for controlling the hydraulic motors 171 in connection with the vertical movementwith ofthe ram 19. The control valve 181 is formed with a small diameter bore 183 to which the pipe 179 is connected and is furtherformedwitha large diameter bore 185 which is connected with the small diameter bore 183. The control valve 181 is provided with a spool 187 which is slidably inserted in the large diameter bore 185 in such a manner as to be movably to connect and disconnect the small diameter bore 183 and the large diameter bore 185.The spool 187 is provided with a stem 189 slidably projecting out of the control valve 181 through a boreformedtherethrough, and itis biased by a spring 191 to disconnect the small diameter bore 183 and the large diameter bore 185 and urge the stem 189 outwardly. The stem 189 of the spool 187 is provided at its outer end with a cam follower 193 which is rotatably disposed in rolling contact with a cam 195 which is provided on the ram 19. The arrangement is such that the spool 187 is moved againstthe spring 191 by the cam 195 by means of the cam follower 193 and the stem 189 to connect the small diameter bore 183 and the large diamter bore 185.Also, the cam 195 is so arranged so as to cause the spool 187 to connectthe small diameter bore 183 and the large diameter bore 185 when the ram 19 is in the proximity of its upper limit.

As shown also in Figure 6, the large diameter bore 185 of the control valve 181 is connected to a pipe 197 which leadsto an accumulator 199 and to a hydraulic source Pvia check valve 201. There is a reliefvalve 203 connected to the pipe 197, and also a cock 205 is provided in parallel with the relief valve 203 to manually drain the hydraulic fluid from the pipe 197.

In the above described arrangement, the spool 187 ofthe control valve 181 is kept pushed against the spring 191 bythecam l95andthecamfollowerl93 to connect the large diameter bore 185 to the small diameter bore 183, when the ram 19 is at its uppermost limit. Therefore, when the ram 19 is at its uppermost limit, the hydraulic motors 171 will be supplied with the hydraulicfluid from the accumulator 199 and the hydraulic source Pthrough the control valve 181 to holdthe hold-up members 149 on a level with the lower blade 15 so thatthe work-sheet W to be sheared may be horizontally placed thereon.When the ram 19 is lowered to enable the upper and lower blades 17 and 15 to shear thework-sheetW,the hold-up members 149 will be pressed by the upper blade 17to be lowered together with the workpiece sheared from the work-sheet W.

When the hold-up members 149 are pressed by the upper blade 17, the piston rods 173 of the hydraulic motors 171 will drive and cause the hydraulic fluid to drain through the control valve 181 against the spool 187 and the spring 191 into the accumulator 199 and the hydraulic source P through the relief valve 203 to enable the hold-up members 149 to be lowered.

When the ram 19 is be raised after the work-sheetW has been sheared, the hold-up members 149 will be kept lowered without raising the workpiece sheared from the work-sheetW, since the spool 187 ofthe control valve 187 has been released from the pressure ofthe cam 1 95 to disconnect the small diameter bore 183 and the large diameter bore 185.

Also, when the ram 19 is returned to its uppermost limit, the cam 195 will push the spool 187 ofthe control valve 181 by means of the cam follower 193 to supplythe hydraulic fluid from the accumulator 199 andthe hydraulicsource P intothe hydraulic motors 171 so thatthe hold-up members 149 can be raised for the next shearing. It is to be noted that pneumatic motors connceted with a pneumatic source can be employed instead ofthe hydraulic motors 171 to enbody the principles ofthe present invention.

Claims (22)

1. A machine tool which comprises a movable ram, means for guiding the ram, and means for maintaining engagement between the ram and the guide means.

2. A machine tool according to Claim 1, wherein the means for maintaining engagement between the ram and the guide means comprises means for urging the guide means into contact with the ram.

3. A machine tool according to Claim 1 or2, wherein the means for maintaining engagement between the ram and the guide means comprises resilient biassing means.

4. A machine tool according to Claim 3, wherein the resilient biassing means comprises spring means.

5. A machine tool according to any of the preceding claims, wherein the means for maintaining engagement between the ram and the guide means comprises means for urging the ram into contact with the guide means.

6. A machine tool according to Claim 5, wherein the means for urging the ram into contact with the guide means comprises means for driving the ram to perform an operation on a workpiece.

7. A machine tool according to Claim 6, wherein the ram is vertically movable and the guide means comprises upper and lower rear guide means for guiding the rear ofthe ram and front guide meansfor guiding the front ofthe ram, and wherein the driving means connected to the rear of the ram above the lower rear guide means.

8. A shearing machine comprising a frame, a work-table which is fixed to or integral with the frame, a lower blade detachably mounted on the worktable, a vertically movable ram for holding an upper blade for performing shearing operations in cooperation with the lower blade, upper and lower rearguide means provided on the frameto guidethe rear of the ram, front guide means provided on the frametoguidethefrontoftheram,driving meansfor driving the ram, the driving means being provided beneath the ram but slightlyto the rear of the plane of vertical movement ofthe ram, and a connecting rod connecting the driving means to the ram, which connecting rod is connected to the ram at a point which is higherthan the lower rear guide means.

9. A shearing machine according to Claim 8, wherein the lower rear guide means are lower than the top surface oftheworktable.

10. A machine tool according to any of the preceding claims, wherein the guide means for guiding the ram comprise rollers.

11. Amachinetool accordingtoanyoneof Claims 1 to 9, whereinthe guide meansforguiding the ram comprisesslidable members.

12. Amachinetool comprising hydraulicand/or pneumatic means for holding down a sheet workpiece to be processed, wherein the hydraulic and/or pneumatic means includes means for supplying a largeramountoffluid under lower pressure, meansforsupplying a smalleramountof fluid under higher pressure, and surge-damping means.

13. Amachinetool according to Claim 12, wherein the hydraulic and/or pneumatic means includes a piston and cylinderarrangement,the meansforsupplying a largeramountoffluid under lower pressure consisting of a larger diameter piston, and the meansforsupplying a smaller amount of fluid under higher pressure consisting of a smaller diameter piston.

14. Amachinetool according to Claim 12 or 13, wherein the surge damping means consists of a slidable large diameter piston.

15. A shearing machine comprising a frame, a work-table fixed to or integral with the frame, a lower blade detachably mounted on the work-table, a vertically movable ram for holding an upper blade for performing shearing operations in cooperation with the lower blade, hydraulic or pneumatic means for holding down a workpiece at or near the front of the frame, the hydraulic or pneumatic means being connected by a passage to pump means and the pump means being provided with means for supplying a larger amount offluid under lower pressure, meansforsupplying a smalleramountof fluid under higher pressure and surge-damping means.

16. A machine tool comprising a plurality of pressing means for pressing upwardly on the lower surface of a workpiece to be processed, wherein the pressing means can be moved up and down and/or tilted.

17. A shearing machine comprising a frame, a work-table fixed to or integral with the frame, a lower blade detachably mounted on the work-table, a vertically movable ram for holding an upper blade for performing shearing operations in cooperation with the lower blade, a plurality of pressing means disposed in a row behind the lower blade for pressing upwardly on a workpiece to be sheared, wherein the pressing means are kept upwardly biassed and can be moved up and down and tilted in accordance with the movementofthe upper blade.

18. A machine tool according to Claim 16 or 17, wherein the pressing means are pivotally connected to one another and are upwardly biassed by a plurality of hydraulic and/or pneumatic means and are arranged so as to begin to be raised afterthe commencement of a processing operation.

19. Amachinetool comprising a work-table, a back-gauge which is movable in the plane of the work-table, and cam means for swinging the back-gauge out of the said plane, the position ofthe cam means being adjustable in accordance with the position ofthe back-gauge.

20. A shearing machine comprising a frame, a work-tablefixed to or integral with the frame, a lower blade detachably mounted on the work-tabie, a vertically movable ram for holding an upper blade for performing shearing operations in cooperation with the lower blade, a back gauge mounted on the carrier means, the carrier means being horizontally movable on rails behind the upper and lower blades and swingable relative to the rails, and cam means adjustably provided on the rails for causing the back gauge to swing away from the level of the top surface of the work-table.

21. A shearing machine, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

22. Any novel feature or combination offeatures described herein.

Amendments to the claims have been filed, and have th.e following effect: (a) Claims 1-7, 10-20 above have been deleted.

(c) Claims 8,9,21,22 above have been re-numbered as 1-4 and their appendancies corrected.