GB2188578A - Shearing machine - Google Patents

Abstract

A shearing machine (1, Fig.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). Hold down means 103 are supplied with fluid by a pump 115 driven from the ram dive shaft 55 via a cam 117. Initially piston 129 is moved through its complete stroke against springs 139, 141 to deliver a relatively large amount of low pressure fluid to cylinders 105. Then piston 131 is moved against spring 141, to deliver less fluid at higher pressure, completing its stroke just as the ram is lowered, the spring 141 damping the surge which occurs in the fluid circuit when the hold down members 109 engage the work. The work may rest on vertically movable and/or tiltable fluid-biassed supports (149). An adjustable back gauge (77) may be provided. <IMAGE>

Description

SPECIFICATION Shearing machine This invention relates to a shearing machine having a pairofupperand lower shearing blades for cutting or shea ring sheet-like materials such as sheet metals.

Asiswellknown,ashearing machineforshearing sheet-like materials such as sheet metals comprises a pairofopposed upright plates, a pairofelongate upperandlowershearing 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 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 machinesisthatthe hydraulicorpneumaticmeansforholding 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.

Afurther disadvantage of conventional shearing machines is that the back gauge means are in the way when a workpiece isto be sheared into an irregular size without using the back gauge means while other workpieces are being continuously sheared into a certain size.

It is an object of the present invention to enable the provision of a 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 fortroublesome adjustment. In one aspect of the invention, therefore, a shearing machine is arranged sothatthe 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 theworkpiece. To attainthis object,a hydraulic pump meansforthehold-down means is provided with a large diameter piston which can supply a Iargeamountoffiowunderlow 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 isprovidedwith meansforholding uptheworkpiece being sheared to preventtheworkpiecefrom bending and curling.

The invention also enables the provision of a shearing machine with a backgaugewhich 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 workpieceto 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, Figure2 is a sectional view taken along the line Il-Il of Figure 1, Figure3 is a diagrammatic view of a hydrauliccircuit of the shearing machine of Figures 1 and 2, Figure4is an enlarged sectional view taken along the line IV-IV of Figure 12 with portions omitted, Figure 5is a sectional view taken along the line V-V of Figure 4, and Figure 6is a diagrammatic view of a different hydraulic circuit.

Referring to Figures 1 and 2, a shearing machine 1 comprisesapairofupright 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 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, ofthe upright plates 3 and 5, and the beam member 11 is horizontally fixed between the rearward top portions ofthe 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 asto cooperate with each other to shear the work-sheetWwhen the ram 19 is lowered to lowerthe 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 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 ofthe ram 19 below the level ofthetop surface of the work-table 13.

As shown in Figure2, in ordertoguidethevertical 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 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, of the ribs 21 of the ram 19 in such a manner as to extend longer than the stroke length ofthe ram 19. The upper and lower guide rollers 27 and 29 freely rotatably dis- posed 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 ofthe 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 upperand lower guide plates 23 and 25. Also, the shafts 33 for the 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 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 pairoffront guide plates 35 are vertically fixed to the front surface of the ram 19, and a pair offront guide rollers 37 are provided on the upper front plate 7 in rolling contact wfth the front guide plates 35. Each ofthe 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 ofthe 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 orderto keep the respectivefrontguide rollers 37 in contact with the respective front guide plates 35, an adjusting bolt 47 is horizontally dis- posed on the box nut 45 to extend horizontallytoward the holding means 41, and a spring 49 is disposed around the bolt 47 to bias the holding member 41 rearwadly. Thus, the front guide rollers 37 are biased bythe respective spring 49 into rolling contact withthefrontguide plates 35 to bias the ram 19to 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 ofthefront guide rollers 37 and thefrontguide 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 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 of the 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 dis posedinthesame mannerasthefrontguiderollers 37 to cooperate with the side guide plates 51 to hold and stop the ram 19from 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 awayfrom 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 ofthe ram 19 by the springs 49, and therefore there is no problem aboutthe 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 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 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 mannerto 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 ofthetop surface ofthe work-table 13 but at a higher level than the point C where the lower guide rollers 29 will be in rolling contact with the lower guide plates 25. More particularly, the connecting rods 65 are pivotally con nected to the eccentrics 61 and are pivotally connected to the ribs 21 ofthe ram 19 bythe 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 componentllaboutthe point Cwhere the lower guide rollers 29 will be in rolling contact with the lower guide plates 25, since the pins 67 are locatedhigherthanthepoint C. Also, the upper blade 17 will be subject to a vertical upward shearing resistance or reaction and a horizontal rearward componentwhen shearing thework-sheetW in cooperation with the lower blade 15. Accordingly, the ram 19, when lowered by the driving shaft 55 and the eccentrics 61,wiII be urged rearward to press the upperand 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 orderto enablethe ram 19to 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 bracket73 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 orderto set the widths or lengths into which the work-sheet W is to be sheared, an elongate back gauge 77 is horizontally provided atthe 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 horizont allytoward and away from the lower blade 15. The carriers 79 are movably mounted, by means ofthe rollers 81,on rails83which are disposed on elong agesupporting members 85 at rightanglestothe upper blade 17.The supporting members 85 are mounted in parallel with each other on the underside of a plate-like base member87which is horizontally fixed to the lower rear end ofthe ram 19 at right an glesthereto 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 ofthe nut members 91.Thecar- riers 79 are pivotally connected to the nut members 91 by means of pins 93 in a mannersuch that it can be swung upward aboutthe pins 93 awayform 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 thatthe rollers 81 will II will ridethereontoenablethecarriers79to 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 shaft99to besimultaneouslydriven bya 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-sheetW 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 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 mov ing 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 longerworkpiece.

Also, it will be understood that the cams 95 can be adjustably moved to any place on the rails 83 so asto 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 upperfront plate 7 in a row to hold the work-sheet Wto be sheared on the worktable 13. Each ofthe hold-down means 103comprises 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 bythe hydraulic fluid against the spring 111 to enablethe hold-down means 103to hold down the work-sheet Wto be sheared onto the work-table 13.

The hold-down means 103 are hydraulically connected bya pipe 113to a pump means 115which is driven by a cam 117 which is coaxiallyfixed to the driving shaft 55 for the ram 19 by a key 1 19 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 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 ofthe largerdiameterbore 123 in axial alignmenttherewith 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. Particularly, the plunger 131 itself is disposed on the inner side of the piston 129, and the stem 133 is slidably inserted in a boreformedthroughthecenterofthe piston 129 in a manner such that the stem 133 is outwardly pro jected from the piston 129. The stem 133 ofthe 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 on the stem 133 of the plunger 131 between the piston 129 and the block 135to 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 ofthe large diameter bore 123 by the cam 117 by means of the 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, afterthe piston 129 has reached the innermost limit, the cam follower 137 will move the plunger 131 inwardly into engage- mentwith the small diameter bore 125 againstthe spring 141 as the cam 117 is further rotated. In this connection,the cam 117 isso arranged that itwill 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 enablethe upper blade 17to sheartheworksheetW in cooperation with the lower blade 15. Also, of the hydraulic fluid is supplied to prevail throughoutthe 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 1 13 by means of a relief valve 145 and a check valve 147. Thus, the hydraulisfluid can be drained from the pipe 113 into the reservoir 143 through the reliefvalve 145 and also can be supplied into the pipe 113 from the reservoir 143 through the checkvalve 147.

in the above described arrangement, each ofthe piston and rods 107 of the hold-down means 103 will be initially moved downwardly by a large amount of hydraulicfluid 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 holddown 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 115 will damp the surge which will occur in the hydraulic ci rcu it when the hold-down members 109 are brought into contact with the work sheetWto hold down it onto the work-table 13. After the piston 129 has reached its innermost limit in the large diameter bore 123 ofthe pump means 115,the plunger 131 will be moved inthesmall diameter bore 125, andthe piston and rods 107 will befurtherurged downwardly by a small amount of hydraulicfluid under high pressure.Thus, the work-sheet W, 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 bytheaction ofthe plunger 131 withoutnoiseand also without being hurt by the hold-down members 109. Also, when the work-sheetW is being held down ontothework-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 55 to enable the upper blade 17 to shear the work-sheetW in cooperation with the lower blade 15.After the work-sheet W has been sheared bythe upper and lower blades 17 and 1S,the driving shaft 55 will raise the ram 19 and rotate furtherthecam 1 17to enablethe cam follower 137 and the springs 141 and 139 to move the plunger 131 and the piston 129 outwardly. After the work-sheetW has been sheared, the piston and rod 107 and the hold-down members 109 will be raised bythe springs 111 to release the work-sheetW as the piston 129 and the plunger 131 are moved outwardly bythe springs 139 and 141. Also, some amount of the hydraulicfluid will sucked intothe pipe 1 13 from the reservoir 143 bythe piston 129 and the plunger 131 which are moved outwardly bythe springs 139 and 141.It is to be noted that pneumatic pump means can be employed instead ofthe hydraulic pump means 115 to embody the principles of the present inven tion. 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 atthe back of the lower blade 15 in parallel therewith to up wardlyhold upthework-sheetWtotheupperblade 17 when the work-sheet W is being sheared by the upper and lower blades 17 and 15. The hold-up memebers 149 are so arranged asto hold uptheworksheetW being sheared in a manner such thatthe 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 angletothe lower blade 15to have a rake angle.

As shown in Figure 4, each ofthe hold-up members 149 is formed at one of its ends with a horizontal cylindrical bore 149b which is partially notched intoa 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 1 49b 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 ofthem can be tilted independentlyofthe otherto comply with the motion of the upper blade 17.

Each ofthehold-up members 149 is fixed bya plurality of bolts 155to one of carrier members 157, each of which is formed at its central portion with a C-shaped opening 157O facing or opening downwardly. The carrier members 157 are disposed atthe backof the lowerfront plate 9 in slidablecontact therewith so that it may be moved up and down and tilted rightward and leftward together with the holdup members 149.In orderto guide the movement of the carrier members 157, an elongate guide plate 159 is horizontallyfixed to the back of the Iowerfront plate 9 bya plurality of bolts 161 by means of a plura lity 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 ofthe 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 lowerfront plate 9 and also between the spacer blocks 163to 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 Iowerfront 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 Ieftward by the hydraulic motors 171 by means ofthe carrier members 157 to hold upthework-sheetW being sheared in compliance with the movement of the upper blade 17.In this connection, the hydraulic motors 171 are so arranged as to holdthehold-up members 149 on a level with the lower blade 15so that the work-sheet W to be sheared may be horizontally placed on the lower blade 1 Sand 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 isslidably inserted in the large diameter bore 185 in such a mannerasto be movably to connectanddis- connect 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 itis biased by a spring 191 todisconnectthesmalldia- meter 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 bythecam 195 by means of the cam follower 193 and the stem 189 to connectthe small diameter bore 183 and the large diamter bore 185. Also, the cam 195 is so arranged asto 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.

Asshown also in Figure6,thelargediameterbore 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 checkvalve 201. There is a relief valve 203 connected to the pipe 197, and also a cock 205 is provided in parallel with the reliefvalve 203 to manu allydrainthe hydraulic fluid from the pipe 197.

In the above described arrangement, the spool 187 ofthe control valve 181 is kept pushed againstthe 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 besupplied with the hydraulic fluid from the accumulator 199 and the hydraulic source Pthrough the control valve 181 to hold the hold-up members 149 on a level with the lower blade 15 so that the work-sheet Wto 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 the work-sheetW, the hold-up members 149 will be pressed by the upper blade 17 to be lowered together with the workpiece sheared from the work-sheet W. When the hold-up members 149 are pressed bythe upper blade 1 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 hydraulicsourcePthroughthereliefvalve203toen- able 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 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 195will push the spool 187 of the control valve 181 by means of the cam follower 1 93 to supply the hydraulicfluid from the accumulator 199 and the hydraulic source P intothe hydraulic motors 171 so thatthe hold-up members 149 can be raised forthe next shearing. It is to be noted that pneumatic motors connceted with a pneumatic source can be employed instead of the hydraulic motors 171 to embody the principles ofthe present invention.

Claims (22)

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

2. Amachinetool according to Claim 1,wherein the means for maintaining engagement between the ram and the guide means comprises meansfor 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 maintain- ing engagement between the ram and the guide means comprises means for urging the ram into con- tact 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. Amachinetool according to Claim 6,wherein the ram is vertically movable and the guide means comprises upper and lower rear guide meansfor guiding the rear of the ram and front guide meansfor guiding the front of the 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 rear guide means provided on the frame to guide the rear of the ram, front guide means provided on the frameto guidethefront ofthe ram, driving meansfor 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 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 one ofthe 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 compriseslidable 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 offluid under higher pressure, and surge-damping means.

13. Amachinetool according to Claim 12, wherein the hydraulic and/or pneumatic means includes a piston and cylinder arrangement, the means forsupplying a largeramountoffluid 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. Ashearing machinecomprisingaframe,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 upperbladefor performing shearing operations in cooperation with the lower blade, hydraulic or pneumatic means for holding down a workpiece at or near the front ofthe 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, means forsupplying asmalleramountoffluid underhigher pressure and surge-damping means.

16. A machine tool comprising a plurality of pressing means for pressing upwardly on the lower sur faceofaworkpieceto 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 machinetool according to Claim 16or 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 com mencementofa 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 backgauge out of the said plane, the position of the cam means being adjustable in accordance with the position ofthe 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 ver ticallymovable ram for holding an upperbladefor 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 ofthetop surface ofthe work-table.

21. A shearing machine, substantially as here- in before 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 the following effect; (a) Claims 1-11,19,20 above have been deleted.

(c) Claims 12-18,21,22 above have been re-numbered as 1-7,8,9. and theirappendancies corrected.