GB2150482A - 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 means for maintaining engagement between the ram and the guide means. Drive means 55 for the ram may be connected to the rear of the ram (19) at a point above the lower rear guide means (29) to maintain said engagement. Alternatively or additionally a spring 49 associated with the front guide means serves to maintain engagement between the ram and the rear guide means. Variable fluid pressure hold down means 103 may be provided. The work may rest on vertically movable and/or tiltable fluid-biassed supports 149. An adjustable backgauge 77 may be provided. <IMAGE>

Description

SPECIFICATION Shearing machine This invention relates to a shearing machine having a pair of upper and lower shearing blades for cutting or shearing sheet-like materials such as sheet metals.

As is well known, a shearing machine for shearing sheet-like materials such as sheet metals comprises a pair of opposed upright plates, a pair of 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 worktable 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 at the front of the shearing machine to hold the workpiece to 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 machines is that the hydraulic or pneumatic means 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 the workpiece may be damaged.

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

A further disadvantage of conventional shearing machines is that the 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 shearing machine whereby the 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 for troublesome 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 means for the 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 of flow 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. For this purpose, the shearing 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 1 is a front elevational view of a shearing machine in accordance with the present invention, Figure 2 is a sectional view taken along the line Il-Il of Figure 1, Figure 3 is a diagrammatic view of a hydraulic circuit of the shearing machine of Figures 1 and 2, Figure 4 is an enlarged sectional view taken along the line IV-IV of Figure 2 with portions omitted, Figure 5 is a sectional view taken along the line V-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 1 comprises a pair of upright plates 3, 5, an upper front plate 7, a lower front 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 lower front plates 7 and 9 and the beam member 11. The upper and lower front plates 7 and 9 are vertically fixed to the upper and lower front portions, respectively, of the upright plates 3 and 5, and the beam member 11 is horizontally fixed 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 lower front plates 9 in such a manner as to frontward project so that a work-sheet W to be sheared can be fed thereon.

As shown also in Figures 1 and 2, an elongate lower blade 15 is detachably fixed horizontally to the back edge of the work-table 13 on the top of the lower front plate 9, and also an elongage upper blade 17 is detachably fixed to 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 other to shear the work-sheet W when the ram 19 is lowered to lower the upper blade 17. Particularly, the ram 19 is a square plate-like member which is formed at its lower end with an elongate slope, and the upper blade 17 fixed aslant to 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 of the ram 19 below the level of the top surface of the work-table 13.

As shown in Figure 2, in order to guide the vertical movement of the ram 19, a pair of upper guide plates 23 and a pair of lower guide plates 25 are fixed to the ribs 21 of the ram 19, and a pair of upper guide 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, of the ribs 21 of the 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 that they will be always kept in rolling contact with the upper and lower guide plates 23 and 25, respectively, when the ram 19 is vertically moved. The shafts 31 and 33 of the guide rollers 27 and 29 are horizontally held on the upper and lower portions, respectively, of the upright plates 3 and Sin vertical alignment with each other to keep always the upper an lower guide rollers 27 and 29 in contact with the upper and lower guide plates 23 and 25.

Also, the shafts 33 for the lower guide rollers 29 are so provided that the 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 of the work-table 13 as designated by C.

In orderto keep the upper and lower guide plates 23 and 25 in contact with the upper and lower guide rollers 27 and 29, a pair of front guide plates 35 are vertically fixed to the front surface of the ram 19, and a pair of front guide rollers 37 are provided on the upper front plate 7 in rolling contact with the front guide plates 35. Each of the front 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 upper front plate 7 and is covered by a box nut 45.Also, in order to 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 member 41 rearwardly. Thus, the front guide rollers 37 are biased by the respective spring 49 into rolling contact with the front guide plates 35 to bias the ram 19 to keep the upper and lower guide rollers 27 and 29 in rolling contact with the upper and lower guide plates 23 and 25 so that the 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 employed, although two sets of them have been described as employed in the preferred embodiment.

Referring again to Figure 1, in orderto prevent the 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 of the ram 19, and a pair of side guide rollers 53 are provided on the upright plates 3 and 5 in 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 by the upper and lower guide rollers 27 and 29, the front guide rollers 37 and the side guide rollers 53 when it is moving vertically to 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 of the ram 11. In this connection, however, it will be understood that some antifriction members can be employed instead of the guide rollers 27, 29, 37 and 53 to cooperate with the guide plates 23,25,35 and 51.

Referring further to 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 9 is vertically moved. The driving shaft 55 is held by the upright plates 3 and 5 by means of bearing means 57, and it is connected to a driving motor 59 in a conventional manner to drive the ram 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 of the top surface of the work-table 13 but at a higher level than the point Cwhere the lower guide rollers 29 will be in rolling contact with 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 componentHwill 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 guide rollers 29 will be in rolling contact with the lower guide plates 25, since the pins 67 are located higher than the point C. Also, the upper blade 17 will be subject to a vertical upward shearing resistance or reaction and a horizontal rearward component when shearing the work-sheet W 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 25 to 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 bias the 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 as to stop the work-sheet W which is fed over the lower blade 15.

The back gauge 77 is carried by a plurality 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 of the rollers 81, on rails 83 which 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 rear end of the ram 19 at right angles thereto in a cantilever manner. In order to 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 members 91 by means of pins 93 in a manner such that it can be swung upward about the pins 93 away form 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 carriers 79 to be swung upward about the pins 97.

More particularly, the cams 95 are so arranged as to be fitted 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 by a motor 101 to move the carriers 79 by means of the 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 is to be sheared. Also, when the rollers 81 of the carriers 79 are brought onto the cams 95 on the rails 83, the carriers 79 will be upwardly swung about the 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 that the work-sheet W can be moved further rearward to be sheared into a wider or longer workpiece. Also, it will be understood that the 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 row to hold the work-sheet W to 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 hydraulic fluid against the spring 111 to enable the hold-down means 103 to hold down the work-sheet W to be sheared onto the work-table 13.

The hold-down means 103 are hydraulically connected by a pipe 113 to a pump means 115 which is driven by a cam 117 which is coaxially fixed to the driving shaft 55 for the 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 smaller 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 particularly, the large diameter bore 123 is formed to be outwardly open, the small diameter bore 125 is formed in connection with the innermost end of the larger diameter 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 of the 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.

Particularly, 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 of the piston 129 in a manner such that the 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 for the 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 on the stem 133 of the plunger 131 between the piston 129 and the block 135 to urge the cam follower 137 into rolling contact with the cam 117.

The arrangement is such that the piston 129 is kept stopped from jumping out of the large diameter bore 123 by the cam 117 by means ofthe cam follower 137, the block 135 and the spring 141 and the cam follower 137 will inwardly push the block 135, the stem 133 and the plunger 131 when the cam 117 is rotated by the driving shaft 55. Thus, when the cam 117 is rotated, the cam follower 137 will initially move the piston 129 inwardly against the spring 139 by means of the block 135 and the spring 141 which is stronger than the spring 139 until the piston 129 reaches its innermost limit. Then, after the 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 against the spring 141 as the cam 117 is further rotated.In this connection, the cam 117 is so arranged that it will cause the cam follower 137 to bring the plunger 131 to its innermost limit in the 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-sheet W in cooperation with the lower blade 15. Also, of course the hydraulic fluid is supplied to prevail throughout the large diameter bore 123, the small diameter bore 125, the passage 127, the pipe 113 and all the hold-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 143 through the relief valve 145 and also can be supplied into the pipe 113 from the reservoir 143 through the check valve 147.

In the above described arrangement, each of the piston and rods 107 of the hold-down means 103 will be initially moved downwardly by a large amount of hydraulic fluid under low pressure from the pump means 115 when the piston 129 of the 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 holddown means 103 will lightly hold down the worksheet W to 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 115 will damp the surge which will occur in the hydraulic circuit when the hold-down members 109 are brought into contact with the work-sheet W to hold down it onto the work-table 13.

After the piston 129 has reached its innermost limit in the large diameter bore 123 of the pump means 115, the plunger 131 will be moved in the small diameter bore 125, and the piston and rods 107 will be further urged downwardly by a small amount of hydraulic fluid under high pressure. Thus, the worksheetW, which has been lightly held down onto the work-table 13 under low pressure, will be finally firmly held down by the hold-down members 109 under high pressure by the 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 by the hold-down members 109, the surplus hydraulic fluid 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 55 to enable the upper blade 17 to shear the work-sheet W in cooperation with the lower blade 15. Aterthe work-sheet W has been sheared by the upper and lower blades 17 and 15, the driving shaft 55 will raise the ram 19 and rotate furtherthe cam 117 to enable the cam follower 137 and the springs 141 and 139 to move the plunger 131 and the piston 129 outwardly.

After the work-sheet W 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-sheet Was the piston 129 and the plunger 131 are moved outwardly by the springs 139 and 141. Also, some amount of the hydraulic fluid will sucked into the pipe 113 from the reservoir 143 by the piston 129 and the plunger 131 which are moved outwardly by the springs 139 and 141. It is to be noted that pneumatic pump means can be employed instead of the hydraulic pump means 115 to embody the principles of the present invention.Referring to Figures 2,4 and 5, a train of hold-up members 149, each being an elongate square block, are provided just beneath the upper blade 17 at the back of the lower blade 15 in parallel therewith to upwardly hold up the worksheet W to the upper blade 17 when the work-sheet W 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-sheet W being sheared in a manner such that the work-sheet W 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 as to 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 of the ram 19 at an 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 149b which 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 of the hold-up members 149 can be swung about the joint block 151. Thus, the hold-up members 149 are connected with each other so that each of them can be tilted independently of the other to comply with the motion of the upper blade 17.

Each of the 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 of the lower front plate 9 in slidable contact therewith so that it may be moved up and down and tilted rightward and leftward together with the hold-up members 49. In orderto guide the movement of the carrier members 157, an elongate guide plate 159 is horizontally fixed to the back of the lower front 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 of the lower front plate 9 and also between the spacer blocks 163 to enable the respective hold-up members 149 to comply with the movement of the upper blade 17.

In orderto move the hold-up members 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 lower front 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 by the hydraulic motors 171 by means of the carrier members 157 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 15 so that the work-sheet W to 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 hydraulic fluid.

Referring to Figure 6, the hydraulic motors 171 are connected by a pipe 179 to a control valve 181 for controlling the hydraulic motors 171 in connection with the vertical movement with of the ram 19. The control valve 181 is formed with a small diameter bore 183 to which the pipe 179 is connected and is further formed with a 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 bore formed therethrough, and it is 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 diameter bore 185. Also, the cam 195 is so arranged as to cause the spool 187 to connect the 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 leads to an accumulator 199 and to a hydraulic source P via check valve 201. There is a relief valve 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 of the control valve 181 is kept pushed against the spring 191 by the cam 195 and the cam follower 193 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 hydraulic fluid from the accumulator 199 and the hydraulic source P through the control valve 181 to hold the hold-up members 149 on a level with the lower blade 15 so that the 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 shearthework-sheetW,the hold-up members 149 will be pressed by the upper blade 17 to be lowered together with the workpiece sheared from the worksheet 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-sheet W has been sheared, the hold-up members 149 will be kept lowered without raising the workpiece sheared from the work-sheet W, since the spool 187 of the control valve 187 has been released from the pressure of the cam 195 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 of the control valve 181 by means of the cam follower 193 to supply the hydraulic fluid from the accumulator 199 and the hydraulic source P into the hydraulic motors 171 so that the hold-up members 149 can be raised for the next shearing. It is to be noted that pneumatic motors connected with a pneumatic source can be employed instead of the hydraulic motors 171 to embody the principles of the 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 or 2, 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 one 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 of the ram and front guide means for guiding the front of the ram, and wherein the driving means is 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 rear guide means provided on the frame to guide the rear of the ram, front guide means provided on the frame to guide the front of the ram, driving means for driving the ram, the driving means being provided beneath the ram but slightly to the rear of the plane of vertical movement of the 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 higher than the lower rear guide means.

9. A shearing machine according to Claim 8, wherein the lower rear guide means are lowerthan the top surface of the worktable.

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

11. A machine tool according to any one of Claims 1 to 9, wherein the guide means for guiding the ram comprise slidable 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 larger amount of fluid under lower pressure, means for supplying a smaller amount of fluid under higher pressure, and surge-damping means.

13. A machine tool according to Claim 12, wherein the hydraulic and/or pneumatic means includes a piston and cylinder arrangement, the means for supplying a larger amount of fluid under lower pressure consisting of a larger diameter piston, and the means for supplying a smaller amount of fluid under higher pressure consisting of a smaller diameter piston.

14. A machine tool 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 of fluid under lower pressure, means for supplying a smaller amount of 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 movement of the 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 after the commencement of a processing operation.

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

20. 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 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 of features described herein.