FR2554372A1 - SHEAR - Google Patents

Abstract

IN A SHEAR 1 INCLUDING A LOWER BLADE 15, A SLIDER 19 CARRYING THE UPPER BLADE 17, UPPER AND LOWER REAR GUIDING MEANS 27, 29 OF THE FRAME, FRONT GUIDING MEANS 67 OF THE FRAME, DRIVING MEANS ARE PROVIDED 55 OF THE SLIDER 19 LOCATED UNDER THE SLIDER 19 SLIGHTLY BEHIND ITS VERTICAL MOVEMENT PLANE AND THE CONNECTING RODS 65 CONNECTED TO THE SLIDER 19 AT A POINT HIGHER THAN THE LOWER REAR GUIDING MEANS 29. TO HOLD THE SHEARING SHEET CYLINDERS CONNECTED TO A PUMP WHICH CAN PROVIDE A LARGE FLOW UNDER LOW PRESSURE AND A SMALL FLOW UNDER HIGH PRESSURE. UPPER HOLDING MEANS 149 OF THE SHEARING SHEET ARE PROVIDED AT THE REAR OF THE LOWER BLADE 15; THEY CAN RISE AND LOWER AND TILT DEPENDING ON THE MOVEMENT OF THE UPPER BLADE. A PIGE CAN, USING 95 CAMS, FREE THE LEVEL OF THE TABLE TO ALLOW THE SHEARING OF AN OVERSIZED SHEET.

Description

Z5543? 2

DESCRIPTION

SHEAR

  The present invention relates to a shear comprising a pair of upper and lower blades for cutting or shearing

  sheet-like materials such as metal sheets.

  As is well known, the shears for shearing materials

  sheet metal like metal sheets has a pair of opposite vertical uprights, a pair of upper and lower blades

  of elongated shape and a table on which the sheet metal is sheared-

  ler and it is maintained for shearing. The lower blade is fixed horizontally to the table and the upper blade is held by a slide arranged to have an up and down movement between the

  uprights to move the upper blade towards the lower blade

  and away from the bottom blade. Also, some

  number of holding means in the form of hydraulic cylinders or tires-

  materials are provided at the front of the shears to keep the sheet at

  shear on the table and moreover a rear rod is provided for

  define the widths or lengths according to which the sheet metal must be sheared.

  Another problem with convention shears-

  nelle has been that the hydraulic or pneumatic holding means for holding the sheets to be sheared will, in fact, strike the sheets on the table because of the sudden introduction of high pressure into the holding means. Consequently, it has been very disadvantageous for significant noises to occur when the sheets are held by the holding means and moreover the sheets will be damaged by

the means of maintenance.

  Another disadvantage with conventional shears has been that the sheets, which are wide and long, bend and roll up to take undesirable shapes, because it is not possible to remove them.

  hold perfectly when sheared.

  It was more disadvantageous with regard to the conventional shears] that the rear rod finds the way when it is necessary to shear a sheet metal with irregular dimensions without it being necessary

  freelance, while continuously shearing other sheet metal

some dimensions.

  It is an object of the invention to provide a shear in which the slide can take an up and down movement.

  precise and smooth, by means of a simple and trouble-free layout

  difficult setting. To achieve this object, the shears are arranged so that the slider, when it moves vertically, is guided in an elastic manner by springs and is driven by drive means so as to be kept pushed into contact

guide means.

  It is another object of the invention to provide a shear comprising holding means which can firmly hold the

  sheet during shearing without making noise or damaging the sheet.

  To achieve this object, a hydraulic pump is provided for the

  holding means, comprising a large diameter piston which will

  provide a large flow under low pressure and dampen the pressure tip and a small diameter piston which will provide a small flow

under high pressure.

  It is another object of the invention to provide a shear which can carry out shearing operations to produce fine parts without bending or winding them. For this purpose, the shears comprise means for holding at the top which will hold the sheet upwards during shearing to prevent it from bending or being rolled up. It is another object of the invention to provide a shears

  having a rear rod which can be used to define the

  geurs or the lengths according to which it is necessary to shear the sheet metal but which can clear the way to allow to shear a sheet

in different dimensions.

  Other characteristics and advantages of the invention will be

  better understood on reading the following description of an example

  ple of realization and with reference to the accompanying drawings in which Figure I is a front elevation view of a shear embodying the principles of the invention and it is partially

  shown in section taken along line I-I in Figure 2.

  Figure 2 is a sectional view taken along the line

II-II of Figure 1.

  Figure 3 is a schematic view showing hydraulic means and a circuit of the shears shown in the figures

1 and 2.

  Figure 4 is an enlarged sectional view taken along

  from line IV-IV of Figure 2, with parts removed.

  Figure 5 is a section taken along the line V-V of

Figure 4.

  Figure 6 is a schematic view showing means

hydraulics and a circuit.

  Referring to Figures-1 and 2, they represent a

  shears 1 consisting of a pair of uprights 3 and 5, a top plate

  front front 7, a front bottom plate 9 and a base 11. The uprights 3 and 5 are arranged vertically parallel to each other

  and are connected to each other, to form a part, by means of the plates

  ques upper and lower before 7 and 9 and box spring 11. The

  that upper and lower front 7 and 9 are fixed vertically to the upper and lower front parts, respectively, of the uprights 3 and 5. And the base 11 is fixed horizontally between the upper rear parts of the uprights 3 and 5. Furthermore the shears 1 is provided with a table 13 fixed horizontally to the upper end of the front lower plates 9 so as to come beyond the front

  so that we can bring a sheet W. As shown also

  ment in Figures 1 and 2, a lower blade of elongated shape 15 and fixed horizontally, removably, to the rear edge of the table 13 at the head of the front lower plate 9 and likewise a blade

  upper elongated 17 is removably attached to the slide

  bucket 19 which can move vertically between the uprights 3 and 5.

  As is conventional, the upper and lower blades 17 and are arranged so as to cooperate with each other to shear the sheet metal W when the slider 19 lowers to lower the blade

  upper 17. More particularly, the slide 19 is constituted

  killed by an element of the square section plate type having a slope at its lower end along its length and the upper blade 17 is fixed obliquely so that this slope gives a cutting angle. Similarly, the slider 19 has on its rear edges a pair of vertical ribs 21 projecting symmetrically towards the rear and which also protrude downwards from the lower end of the slider 19, below the level of the upper surface of the

table 13.

  As shown in FIG. 2, to guide the vertical movement of the slide 19, a pair of upper guide plates 23 and a pair of lower guide plates 25 are fixed to the

  ribs 21 of the hatch 19 and a pair of upper guide rollers

  27 and a pair of lower guide rollers 29 are respectively

  vement provided on the shafts 31 and 33. The upper and lower guide plates 23 and 25 are fixed vertically to the upper and lower ends respectively, ribs 21 of the slide

  19 so as to extend further than the length of the stroke of the neck

  wiper 19. The upper and lower guide rollers 27 and 29 are arranged, with the possibility of turning freely, on the shafts 31 and 33 so as to always remain in rolling contact with the upper and lower guide plates 23 and 25, respectively, when the slider 19 moves vertically. The shafts 31 and 33 of the guide rollers 27 and 29 are held horizontally on the upper and lower parts, respectively, of the uprights 3 and 5, in vertical alignment with one another to always keep the upper and lower guide rollers 27 and 29 in contact with the upper and lower guide plates 23 and 25. Similarly the

  shafts 33 for the lower guide rollers 29 are provided so that

  except that the lower guide rollers 29 are in rolling contact

  ment with the lower guide plates 25 at a level lower than that of the upper surface of the table 13 and designated by C. To 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 fixed vertically to the front surface of the slide 19; and a pair of front guide rollers 37 are provided on the front top plate 7 in rolling contact with the front guide plates 35. Each

  front guide rollers 37 is maintained, with the possibility of

  ner freely, by means of a shaft 39 mounted on a support 41 arranged, with the possibility of horizontal displacement, in a bore provided in

  the upper front plate 7. The outer end of the holding means

  yours 41 projecting forward from the front upper plate 7 is arranged so as to be able to move horizontally in a casing 43 fixed to the front upper plate 7 and it is covered by a nut 45. Similarly, to maintain the respective rollers before guide 37 in contact with the respective plates before guide 35, an adjustment screw 47 is disposed horizontally on the box nut so as to extend horizontally towards the holding means 41; and a spring 49 is arranged around the screw 47 to push the holding element 41 backwards. In this way the front guide rollers 37 are pushed by the respective spring 49 to come into rolling contact with the front guide plates

  to push the slide 19 so as to keep the rollers

  laughing and lower guide 27 and 29 in rolling contact with the upper and lower guide plates 23 and 25 so that the slider 19 can take an up and down movement with precision and without shaking. From this point of view it will be understood that it is possible to use a single set of front guide rollers 37 and front guide plates 35, although the two games have been described.

  as used in the preferred embodiment.

  Referring again to FIG. 1, to prevent the slide 19 from being subjected to lateral jerks to the right and towards

  left when moving vertically, a pair of side plates

  guide rails 51 are fixed vertically on both sides of the slide

  bucket 19 and a pair of lateral guide rollers 53 are provided on the uprights 3 and 5 in rolling contact with the lateral plates

  guide 51. The lateral guide plates 51 are arranged exactly

  in the same way as the front guide rollers 37 are for cooperating with the lateral guide plates 51 to maintain the

  slide 19 and protect it from jolts.

  In the arrangement described above, the slide 19 will be maintained and protected from jolts by means of the upper and lower guide rollers 27 and 29, the front guide rollers 37 and the lateral guide rollers 53 during its vertical movement to bring the upper blade 17 towards the lower blade 15 and away from it. Likewise the guide rollers 27, 29, 37 and 53 are held elastically in rolling contact with the guide plates 23, 25, 35 and 51 of the slide 19 by means of the springs 49 and therefore there is no problem with regard to the guide play of the slide 11. From this point of view, however, it will be understood that anti-friction elements can be used in place of the guide rollers 27, 29, 37 and 53 to cooperate with the plates guiding

23, 25, 35 and 51.

  Referring further to Figures 1 and 2, to give the slider 19 an up and down movement, a drive shaft

  is arranged horizontally under the slide 19, between the

  tants 3 and 5. It is important to note that the drive shaft 55 is located under the slider 19 but a little more to the rear than the vertical plane in which the slider 19 travels vertically. drive 55 is held by the uprights 3 and 5 by means of spans 57 and it is connected to a drive motor 59, of

  conventionally, to drive the slide 19. The drive shaft

  track 55 has at its opposite ends a pair of eccentric

  ques 61, which are fixed to it by a key 63 and the eccentrics 61

  are connected, by respective connecting rods 65, to the ribs 21 of the slide

  bucket 19 by means of respective axes 67. More importantly, the axes 67 of the connecting rods 65 are located at a level lower than that of the upper surface of the table 13 but at a level higher than that of the point

  C o the lower guide rollers 29 will be in rolling contact

  ment with the lower guide plates 25. More particularly,

  the connecting rods 65 are connected, with the possibility of pivoting, to the excen-

  triques 61 and are connected, with the possibility of pivoting, to the ribs 21 of the slide 19 by means of the axes which are aligned horizontally

  with each other. Thus, when the drive shaft 55 is entrained

  born by the drive motor 59, the eccentrics 61 will give the slide 19 an up and down movement by means of the connecting rods 65

and axes 67.

  In the arrangement described above, a vertical component VE and a horizontal component H will act on the axes 67 of the connecting rods

  when the slide 19 lowers under the action of the drive shaft

  55 and eccentrics 61. Thus the slider 19 will tend to tilt clockwise in FIG. 2 under the action of the moment of the horizontal component H relative to the point C o the rollers

  lower guide 29 will be in rolling contact with the

  the lower guide 25, because the axes 67 are located higher than the point C. Likewise, the upper blade 17 will be subjected to a resistance or a vertical shear reaction directed upwards and to a horizontal component directed towards the rear when it shears the sheet W in cooperation with the lower blade 15. Consequently the slide 19, when it is lowered by the shaft

  drive 55 and the eccentrics 61, will be pushed backwards

  to push the upper and lower guide plates 23 and in the direction of the upper and lower guide rollers 27 and

  29 to lower without shaking to lower the upper blade 17.

  As can also be seen in FIG. 2, a balancing means 69, shown in the preferred embodiment in the form of a pneumatic cylinder, is provided to intervene on the slide 19

  in the direction directed vertically and backwards to allow

  to slide 19 to go up smoothly. More specifically,

  the balancing means 69 are connected, with the possibility of pivoting-

  ment, at their upper end, by an axis 71 to the base 11 by means

  of a gusset 73 and they are also connected, at their lower end

  superior, to a gusset 75 fixed to the slide 19. Thus, not only the slide 19 can go up smoothly but it can also be done

  up and down with precision, the upper and lower plates

  guide rails 23 and 25 being kept in contact with the rollers

  upper and lower guide 27 and 29.

  As shown in FIG. 2, to define the widths or the lengths according to which the sheet W must be sheared, a rear rod of elongated shape 77 is provided, arranged horizontally, behind the upper and lower blades 17 and 15, in parallel to them, so as to serve as a stop for the sheet metal W which is brought over the lower blade 15. The rear rod 77 is carried by a number of supports 79 each comprising rollers 81, so

  that it can move horizontally as it gets closer and farther away

  of the lower blade 15. The supports 79 are mounted movable, by means of rollers 81, on the rails 83 arranged on support elements, of elongated shape 85, at right angles to the upper blade 17. The support elements 85 are mounted parallel to each other on the underside of a base element, plate type, 87 fixed horizontally to the rear lower end of the slide

  19, at right angles to it, overhanging.

  To move the supports 79 on the rails 83, lead screws 89 having nuts 91 are provided with the possibility of rotation, on the support elements 85 and are connected to the supports 79 by means

  nuts 91. The supports 79 are connected with the possibility of pivoting-

  ment, to the nuts 91 by means of axes 93 so as to be able to tilt upwards around the axes 93 away from the level o moves

  horizontally the sheet metal W to be sheared. Similarly, cams 95 are pre-

  seen on the rails 83, near their rear ends, so that the rollers 81 rise therein to allow the supports 79 to tilt upwards around the axes 93. More particularly, the cams 95 are arranged so as to be stay in a number

  bores on the rails 83 so as to be able to be positioned in an amo-

  visible, anywhere on rails 83, at will. The lead screws 89 are connected to each other by means of gear boxes and of a shaft 99 to be simultaneously driven by a motor 101 for

  move the supports 79 by means of the nuts 91.

  In the arrangement described above, the rear rod 77 will move horizontally in the direction of, and away from, the lower blade 15 with the supports 79 under the action of the lead screws 89

  and nuts 91 to define the widths or lengths according to-

  which it is necessary to shear the sheet W. Similarly, when the rollers 81 of the supports 79 are brought onto the cams 95 which are on the rails 83, the supports 79 will pivot upwards around the axes 93 to put the rear rod 77 out of the path corresponding to the level in which the sheet W moves horizontally. Thus, we can raise the rod

  rear 77 by moving the supports 79 on the cams 95 by doing them

  sant get out of the rails 83 so that you can continue to push the sheet W backwards to shear it to make a more

  wide or longer. It must also be understood that one can soul-

  ner, for adjustment, the cams 95 in all places of the rails 83 so as to be able to raise the rear rod 77 out of the way in all

  desired positions on the rails 83.

  Referring to Figure 3 in addition to Figures 1 and 2, we see that a number of holding means 103 are mounted on the

  lower part of the upper front plate 7, in file, for hand-

  hold the sheet W to be sheared on table 13. Each of the means of main-

  tien 103 has a hydraulic cylinder 105, a piston and a rod 107 arranged so that it can slide vertically in the cylinder and comprising at its lower end a retaining element 109, a spring 111 arranged in the cylinder 105 to push the piston and the rod 107 upwards. The arrangement is such that the piston and the rod 107 are pushed down by the hydraulic fluid by acting against the spring 111 to allow the holding means

  103 to maintain on table 13 the sheet W to be sheared.

  The holding means 103 are hydraulically connected by a pipe 113 to a pump 115 driven by a cam 117 fixed coaxially to the drive shaft 55 of the slide 19 by a key 119 so as to rotate with it. The pump 115 consists of a casing 121 comprising a bore 123 of large diameter, a bore

  of small diameter connected to bore 123 of large diameter and a pass-

  sage 127 connecting the small diameter bore and the pipe 113. More

  in particular, the large diameter bore 123 is designed to open

  screw outwards, the small diameter bore 125 is connected with the innermost end of the large diameter bore 123, in axial alignment with it, and the passage 127 is provided to connect the most internal diameter 125 small bore to

driving 113.

  In the casing 121 of the pump 115, a piston 129 of the cup type is arranged, with the possibility of sliding, in the large diameter bore 123 and a plunger 131 having a rod 133 is mounted, with the possibility of sliding, on the piston 129 so

  be able to enter the small diameter bore 125. In particular

  link, the plunger 131 itself is disposed on the internal side of the piston 129 and the rod 133 is inserted, with the possibility of sliding, in a bore provided through the central part of the piston 129 so that the rod 133 comes beyond the outside the piston 129. The rod 133 of the plunger 131 has at its outer end a block 135

  on which a cam roller 137 is arranged, with the possibility of rotation

  tion, in rolling contact with cam 117 on the drive shaft.

  ment 55 of the slide 19. Similarly, a spring 139 is arranged in

  the bore 123 of large diameter to push the piston 129 outwards

  laughing, and another spring 141, stronger than spring 139, is dis-

  placed on the rod 133 of the plunger 131, between the piston 129 and the block, to push the cam roller 137 into rolling contact with the

cam 117.

  The arrangement is such that the piston 129 is prevented from coming out

  firing of the large diameter bore 123 by the cam 117, via

  diary of the cam roller 137 of the block 135 and of the spring 141 and that the cam roller 137 will push inwards the block 135, the rod 133 and the plunger 131 when the cam 117 is rotated by the shaft d drive 55. Consequently, when the cam 117 is rotated, the cam roller 137 will first move the piston 129 inwards by acting against the spring 139 by means of the block 135 and the spring 141, stronger than the spring

  139, until the piston 129 reaches its innermost limit.

  Then, when the piston 129 has reached its innermost limit, the cam roller 137 will move the plunger 131 inward to introduce it into the small diameter bore 125, acting against the spring 141, when the cam 117 continues to rotate. From this point of view, the cam 117 is arranged so that the cam roller

  137 brings the diver 131 to its innermost limit in the area

  sage of small diameter 125 Just before the slide 19 lowers under the action of the drive shaft 55 to allow the blade

  upper 17 to shear the t8le W in cooperation with the lower blade

  15. In addition, of course, the hydraulic fluid is supplied to make the pressure prevail in the large diameter bore 123, in the small diameter bore 125, in the passage 127, in the pipe.

  113 and in all of the holding means 103.

  As can also be seen in FIG. 3, a reservoir 143,

  containing hydraulic fluid, is connected to line 113 via the

  middle of a relief valve 145 and a non-return valve 147.

  Thus the hydraulic fluid can pass from the pipe 113 into the

  servoir 143 via the relief valve 145 and can also be sent in line 113, from the reservoir 143,

  through the non-return valve 147.

  In the arrangement described above, each of the pistons and rods 107 of the holding means 103 will first move downward under the action of a large flow of hydraulic fluid under low pressure, coming from the pump 115, when the piston 129 of the pump

  is moved inward in the large diameter bore 123.

  Consequently, when the piston 129 is moved inwards, the holding elements 109 of the holding means 103 will slightly maintain on the table 13 the sheet W to be sheared, under low pressure, with reduced noise and without damaging the sheet W. In addition, the spring 141 of the pump 115 will absorb the pressure peak which will occur in the hydraulic circuit when the holding elements 109 come into contact with the sheet W to hold it on the table 13. When the piston 129 has reached its innermost limit in the bore of large

  diameter 123 of the pump 115, the plunger 131 will be moved to

  nir in the small diameter bore 125 and the pistons and rods 107 will continue to be pushed down under the action of a low flow of hydraulic fluid under high pressure. Thus the sheet W, which was first slightly held on the table 13 under low pressure, will finally be held firmly by the holding elements 109

  under high pressure, under the action of plunger 131, quietly and evenly

  ment without being damaged by the retaining elements 109. In addition, when the sheet metal W is held on the table 13 by the retaining elements 109, the surplus hydraulic fluid will be entrained in the reservoir via the relief valve 145. Once the sheet W is firmly held by the holding elements 109, the slide

  19 will lower under the action of the drive shaft 55 to allow

  put the upper blade 17 to shear the sheet W in cooperation with the lower blade 15. Once the sheet W shears by the upper and lower blades 17 and 15, the drive shaft 55 will raise the slider 19 and continue to rotate the cam 117 to allow the cam roller 137 and the springs 141 and 139 to move the plunger 131 and the piston 129 outward. Once the sheet W has been sheared,

  pistons and rods 107 and retaining elements 109

  will go under the action of the springs 111 to release the sheet W as and

  as the piston 129 and the plunger 131 are moved outward

  laughed by springs 139 and 141. In addition, a certain amount of

  hydraulic fluid will be drawn into line 113, from the tank

  see 143, under the action of the piston 129 and the plunger 131 which are entraf-

  born outwards by springs 139 and 141. Note that a pneumatic pump can be used instead of the hydraulic pump 115

  to materialize the principles of the invention. Referring to Figures 2, 4 and 5, there is provided a train of holding elements at the top

  149, each consisting of a full square of elongated shape, just between

  below the upper blade 17 at the rear of the lower blade 15, in parallel with the latter, to hold the sheet W upwards towards the upper blade 17 while the upper and lower blades 17 and 15 shear the sheet W. The holding elements 149 are arranged so as to keep the sheet W upwards during the

  shearing so that the sheet W is held or gripped between the elements

  holding elements up 149 and the upper blade 17 as the upper blade 17 lowers. Consequently, the upward holding elements 149 are arranged so as to move up and down and also to tilt to adapt to the movement of the upper blade 17 which is detachably fixed at the end. lower of the slide 19 at an angle with the

  lower blade 15 to have a cutting angle.

  As seen in Figure 4, each of the main-

  yours up 149 has at one of its ends a horizontal cylindrical bore 149b which forms a partial notch of more or less semi-cylindrical shape and these elements are connected to each other by a terminal block 151 s 'adjusting in the bore 149b by means of a screw 153. More particularly, the upward holding elements 149 are spaced apart from each other by a short length and the terminal block 151 is engaged, with adjustment, in the cylindrical bore 149b so that each of the upward retaining elements 149 can pivot around the terminal block 151. Thus, the upward retaining elements 149 are connected to each other so that each of them can switch independently of the others

  to adapt to the movement of the upper blade 17.

  Each of the upward retaining elements 149 is fixed by a number of screws 155 to one of the support elements 157, each of which has in its central part an opening 157o, C-shaped, facing or opening towards the bottom. The support elements 157 are arranged at the rear of the front lower plate 9, in contact

  sliding with it, so you can go up and down and tilt-

  ler to the right and to the left with the retaining elements upwards 149. To guide the movement of the support elements 157, an elongated guide plate 159 is fixed horizontally to the rear of the front lower plate 9 by a number of screws 161, by means of a number of spacer blocks 164 each of which is located between the support elements 157. In addition, one of the support elements 157 is connected, with the possibility of pivoting, to the rear of the lower front plate 9 by a link 165 which pivots at one of its ends on a part of one of the support elements 157 by an axis 167 and which pivots at the other end on an axis 169

  which extends between the guide plate 159 and the rear of the plate

  than lower front 9. Thus the support elements 157 can move up and down and tilt to the right and to the left between the guide plate 159 and the rear of the lower front plate 9 and also between the spacer blocks 163 to allow the elements respective holding up 149 to adapt to the displacement of

the upper blade 17.

  To move the retaining elements upwards 149 upwards and downwards, there are provided under the support elements 157 a certain number of hydraulic cylinders 171 each having a rod

  piston 173 and their piston rods 173 are connected, with possibility

  pivoting unit, to the support elements 157 by axes 175. The hydraulic motors 171 are arranged substantially vertically with their piston rods 173 projecting upwards in connection with the support elements 157 and they are mounted with the possibility of pivoting,

  at the rear of the front lower plate 9 by means of pins 171 in front of

  ower to swing slightly to the right and to the left. In this way the upward holding elements 149 are held,

  moved up and down and also tilted to the right

  te and to the left by the hydraulic motors 171, via

  diary of support elements 157, to hold the sheet upwards

  W during shearing, in accordance with the displacement of the upper blade

  higher 17. From this point of view the hydraulic motors 171 are available

  seated so as to keep the upward holding members 149 level with the lower blade 15 so that the shear w8 can be placed horizontally on the lower blade 15 and on the upward holding members 149 when the rods piston 173 are fully extended to their upper extreme limit

  under the action of hydraulic fluid.

  Referring to Figure 6, the hydraulic cylinders 171

  are connected by a line 179 to a control valve 181 to com-

  apply hydraulic motors 171 in connection with displacement

  vertical of the slide 19. The control tap 181 has a bore

  sage of small diameter 183 to which the line 179 is connected and comprises

  te also a large diameter bore 185 which is connected to the small diameter bore 183. The control valve 181 has a coil 187 inserted, with the possibility of sliding, in the large diameter bore 185 so as to be able, by moving, connecting and separating the small diameter bore 183 and the large diameter bore 185. The

  coil 187 has a rod 189 which slides out of the valve

  control net 181 by a bore formed therein and it is pushed by a spring 191 to separate the bore of diameter 183 and the bore of large diameter 185 and push the rod 189 outside. The rod 189 of the coil 187 has at its outer end a roller

  cam 193 arranged, with possibility of rotation, in rolling contact

  ment with a cam 195 provided on the slide 19. The arrangement is such that the coil 187 moves, acting against the spring 191, under the action of the cam 195 via the cam roller 193

  and rod 189 to connect the small diameter bore 183 and the bore

  sage large diameter 185. In addition, the cam 195 is arranged so

  to cause the coil 187 to connect the bore of small diameter 183 and -

  the large diameter bore 185 when the slide 19 is at

  near its upper limit.

  As also seen 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 source of hydraulic fluid.

  lique P via a non-return valve 201. There is a relief valve 203 connected to the line 197 as well as a plug 205 provided in parallel with the non-return valve 203 to allow

  manually drain the hydraulic fluid from line 197.

  In the arrangement described above, the coil 187 of the robi-

  control net 181 is kept pushed by acting against the spring 191, by the cam 195 and the cam roller 193 to connect the bore of

  large diameter 185 to bore small diameter 183 when the slide

  bucket 19 is at its extreme high limit. Therefore when the

* slide 19 is at its extreme high limit, the hydraulic cylinders

  liques 171 will be supplied with hydraulic fluid from the accumulator

  mulator 199 and the hydraulic fluid source P via

  diary of the control tap 181 to hold the hand-elements

  stand at the top 149 at the level of the lower blade 15 so that the shear t8le W can be placed there horizontally. When the

  slide 19 lowers to allow upper and lower blades

  laughing 17 and 15 to shear the t8le W, the top holding elements 149 will be pushed back by the upper blade 17 to be lowered at the same time as the blank sheared from the sheet W. When the top holding elements 149 are repelled by the upper blade

  17, the piston rods 173 of the hydraulic cylinders 171 will act positively

  and bring the hydraulic fluid out through the net control valve 181, acting against the coil 187 and the spring

  191, to come into the accumulator 199 and the source of hydraulic fluid

  lique P through the relief valve 203 to allow the top holding members 149 to lower. Once the slide 19 has been lowered after shearing the sheet W, the top holding members 149 will remain lowered without lifting the sheared blank from the sheet W, because the coil 187 of the control valve 181 has been released.

  pressure from cam 195 to interrupt the connection between the

  wise of small diameter 183 and the bore of large diameter 185. Likewise when the slide 19 returns to its extreme upper limit, the cam 195 will push the coil 187 of the control valve 181, by means of the roller

  cam 193, to pass the hydraulic fluid from the accumulator

  199 and the hydraulic fluid source 19 in the hydraulic cylinders

  liques 171 so that the top holding elements 149 can be lifted for the next shearing. Note that we can

  use pneumatic cylinders connected to a source of pneumatic fluid

  tick instead of hydraulic cylinders 171 to implement the principles

of the invention.

  Of course various modifications can be made by those skilled in the art to the devices or processes which have just been

  described only by way of nonlimiting example without leaving the case

dre of the invention.

Claims (10)

  1. Shear (1) in which a lower blade (15) is removably attached to a table (13) provided in one piece on the   frame, a slide (19), movable vertically, is provided to maintain   nir an upper blade (17) to execute the shearing operations-   lage in cooperation with said lower blade (15), upper and lower rear guide means (27, 29) are provided on the frame to guide the upper and lower rear parts of the slide (19), front guide means ( 37) are provided on the   frame for guiding the front part of the slide (19), means for   drag (55) for driving the slide (19) are provided under the   slide (19) but slightly further back than the plane of the movement   vertical slider (19) and connecting rod means (65) for the drive means (55) are connected to the slider (19) at a position located at a level higher than the rear lower means guide (29).   2. Shear (1) according to claim 1, in which the   guide means for guiding the slide (19) are rollers (27,29).   3. Shear (1) according to claim 1, wherein the guide means (27, 24) for guiding the slide (19) are   elements allowing sliding.   4. Shears (1) according to claim 1, wherein the lower rear guide means (29) are located below   the upper surface of the table (13).   5. Shear (1) in which a lower blade (15) is removably attached to a table (13) provided in one piece on the   frame, a slide (19), movable vertically, is provided to maintain   nir an upper blade (17) to execute the shearing operations-   beam in cooperation with the lower blade (15), shears in which hydraulic or pneumatic means (105) for holding the sheet W are provided at the front part of the frame (7), in which hydraulic or pneumatic cylinders (105) are connected by a passage to a pump (115) and the pump (115) comprises a means for providing a large flow under low pressure, a means for providing a small flow   under high pressure and a means for absorbing the pressure surge.   6. Shears (1) according to claim 5 wherein the pump (115) comprises a cylinder (121) and a piston (129, 131) in which the means for supplying a large flow rate under low pressure consist of a piston large diameter (129) and the means for supplying a small flow under high pressure consist of a small diameter piston (131).   7. A shear according to claim 5 or claim 6 wherein the means for absorbing the pressure point consists   into a large diameter piston (129) arranged so that it can slide.   8. Shear (1) in which a lower blade (15) is removably attached to a table (13) provided in one piece on the   frame, a slide (19), movable vertically, is provided to maintain   nir an upper blade (17) to execute the shearing operations-   beam in cooperation with said lower blade (15), in which a train of top holding means (149) arranged in a line behind the bottom blade (15) to hold up a   t8le W to be sheared so that these means are kept pushing   seated up and can take a move up and down   and tilting in accordance with the displacement of the upper blade.   9. Shear (1) according to claim 8 wherein the   top holding means (149) are connected, with the possibility of pivoting   together, and are pushed up by a number of hydraulic or pneumatic cylinders (171) and are also arranged to start lifting later than the slider (19). 10. Shear (1) in which a lower blade (15) is removably attached to a table (13) provided in one piece on the   frame, a slide (19), movable vertically, is provided to maintain   nir an upper blade (17) to execute the shearing operations-   lage in cooperation with the lower blade (15), shears in which a rear rod (77) is intended to be movable horizontally thanks to   support means (79) on rails (83) behind the upper blades   lower and lower (17, 15) so as to be able to switch on the   yen supports (79) and in which cam means (95) are   provided on the rails (83) to allow the rear rod (77) to lower   run over the support means (79) leaving the level of the upper surface of the table (13) so that it can be placed, by   adjustment, anywhere on the rails (83).