Machine for bending bar or rod material

The invention concerns a bending machine for bar or rod material such as reinforcement bars for reinforcing concrete. The machine includes a bending mandrel which is stationary during the bending process and a bending tool which can be pivoted about the mandrel. Directly in front of the bending mandrel in the direction of the feed path of the bar or rod material are positioned two clamping cheeks movable relative to one another in a direction perpendicular to the feed path of the material, the cheeks each including a clamping face substantially parallel with the feed path and a cutting face substantially perpendicular to the respective clamping face, the lines of intersection of these faces forming cutting edges substantially parallel with one another. The clamping cheeks are also movable relative to one another in a direction substantially parallel toward the feed path so that they can be displaced from a clamping position in which their respective cutting edges are offset from one another and their clamping faces face one another, into a cutting position in which their cutting edges are aligned and the clamping faces are offset from one another.

For the bending of bar or rod material, in particular of reinforcement bars 
for reinforced concrete construction, it is known to use bending-machines 
which include at least one bending-mandrel which is stationary during the 
bending process, and one bending-tool, e.g., in the form of a 
bending-roller which can be pivoted about this mandrel. Bending-machines 
of this kind are use to produce thrust stirrups, for example, which in 
reinforced concrete construction are necessary in large quantities. 
The production process usually proceeds completely automatically, 
controlled by a programmed controller. 
The bending machine is equipped with a motor-driven feeder which withdraws 
the bar material from a storage reel and a presettable measuring device 
measures the length of the bar material as it is fed forwards and stops 
the feeder as soon as the required length of material has been pulled off 
the reel. A straightener inserted in the feed path of the material, and 
which consists of a number of groups of straightener rolls arranged in 
different planes, straightens the bar material as it is fed forward. As 
soon as a feed step is concluded the actual bending mechanism is 
automatically set in motion to bend the bar through a likewise presettable 
angle, whereupon either a further bending process is initiated by the 
programmed controller or a cutting mechanism arranged near the stationary 
bending-mandrel is actuated to cut the bent rod to length. 
After the cut has been performed another cycle of feeding and bending steps 
is initiated by the programmed controller, which again ends in a cut. A 
machine of this kind is described in the Austrian Patent Specification No. 
314,319. 
With bending-machines of that kind, however, it is not readily possible to 
bend bars having circumferential ribs or circumferential rows of ribs in 
such a way that the bar during bending does not get twisted so that for 
example, in the case of an end product in the form of a closed rectangular 
bar chain as may perhaps be employed as a thrust stirrup for reinforced 
concrete beams, all four sides of the bar chain always lie with certainty 
in one and the same plane. 
In accordance with our earlier proposal (cf. Austrian Patent Application A 
10037/74) undesirable twisting of the bar during bending is prevented by a 
clamping mechanism being provided along the material feed path directly 
before the bending-mandrel which is stationary during the bending process, 
the clamping mechanism being actuable in dependence upon the actuation of 
the pivotable bending-tool and is capable during the time of actuation of 
the pivotable bending-tool, of clamping the barlike material firmly 
against twisting. 
In this earlier proposal it was also further suggested that the stationary 
clamping-cheek of the clamping mechanism should at the same time be formed 
as the stationary blade of a shear used for cutting the barlike material 
to length. 
The present invention is concerned with the problem of equipping a 
bending-mechanism of the kind specified above, with a combined clamping 
and cutting mechanism and in accordance with the present invention the 
clamping-cheeks are movable relative to one another in a direction 
perpendicular to the feed path of the material, the cheeks each including 
a clamping-face substantially parallel with the feed path and a 
cutting-face substantially perpendicular to the respective clamping-face 
the lines of intersection of these faces forming cutting-edges 
substantially parallel with one another, the clamping-cheeks also being 
movable relative to one another in a direction substantially parallel with 
the feed path so that they can be displaced, from a clamping position in 
which their respective cutting-edges are offset from one another and their 
clamping-faces face one another, into a cutting position in which their 
cutting edges are aligned and the clamping-faces are offset from one 
another. 
Preferably, the relative mobility of the two clamping-cheeks with respect 
to one another both in the direction perpendicular to the feed path of the 
bar or rod material and also in a direction substantially parallel with 
this feed path is achieved by the fact that there are provided a lowering 
shaft arranged at a distance from the feed path of the bar or rod material 
and in a direction at right angles to the feed path and, arranged on this 
shaft, an eccentric on which one of the two clamping-cheeks is pivotally 
supported, and devices are provided for pivoting the lowering-shaft about 
its axis as well for pivoting the clamping-cheeks about the eccentric. 
In order to avoid waste of bar material and to be able to work as 
economically as possible it is desirable to sever the bar or rod material 
after the last bending process as close to the last point of bend as is 
possible or respectively is possible according to the required 
specification for the thrust stirrups. It is therefore advantageous to 
arranged the stationary clamping-cheek which is at the same time used as 
the stationary blade, as close as possible to the bending-mandrel during 
the bending process and to form at least the bending-mandrel in such a way 
that it may be withdrawn from the plane of bend so that it does not 
obstruct the clamping-cheek which is used as the moving blade during the 
cutting process. If necessary also the pivotable bending-tool is able to 
shift in the direction perpendicular to the plane of bend and devices are 
provided which are capable of retracting the bending-mandrel and if 
necessary the pivotable bending-tool, out of the plane of bend when the 
clamping-cheeks are brought into the cutting position. 
Although naturally every kind of drive which serves the purpose may be 
applied to the clamping, bending and cutting tools of a bending-machine in 
accordance with the invention, a hydraulic drive proves particularly 
advantageous, wherefore in the case of a bending-machine in accordance 
with the invention hydraulic operating cylinders are preferably provided 
for pivoting the lowering shaft about its axis, for pivoting the 
clamping-cheek about the eccentric and for moving the bending-mandrel and 
if necessary the pivotable bending-tool in the direction perpendicular to 
the plane of bend. 
In order on the one hand not to deform the length of material during the 
bending process by too great clamping forces and on the other hand to be 
able to bring into effect upon the clamping-cheek which is used as the 
movable blade sufficiently large forces for the cut, in accordance with a 
further feature of the invention the piston in the hydraulic operating 
cylinder which pivots the lowering-shaft can at option be acted upon by 
pressure on the face opposite the piston rod, on the face adjacent the 
piston rod or on both faces at once.

The axis of the bar or rod material which is to be bent and the direction 
of motion of the material are indicated in the drawing by an arrow M which 
at the same time also gives the position and direction of the feed path of 
this material inside the bending-machine. 
Underneath the feed path M there is arranged a stationary clamping-cheek 1 
and above it a movable clamping-cheek 2. 
Behind the two clamping-cheeks 1, 2 in the direction of feed of the strand 
of material lies a bending-mandrel 3 which is stationary during the 
bending process and about which a bending-tool 4 which in the embodiment 
illustrated has the shape of a roller, can be pivoted by means of a 
swinging arm 34. Each of the two clamping-cheeks 1, 2 exhibits a 
clamping-face 5, 6 respectively running parallel with the feed path M of 
the strand of material. The clamping-faces 5, 6 form together with 
cutting-faces 7 and 8 respectively running essentially perpendicular to 
them, cutting-edges 9, 10 parallel with one another. 
The movable clamping-cheek 2 is supported so as to be able to pivot about 
an eccentric indicated only by its axis 11, which is arranged on a shaft 
12. The shaft 12 is supported rotatably in the machine frame and is used 
for lowering the movable clamping-cheek during bending and during cutting. 
A hydraulic operating-cylinder 13 hinged to the machine frame at 17 and the 
piston rod 14 of which is hinged to a single-arm lever 15, which is 
connected fixedly in rotation to the lowering-shaft 12, allows the shaft 
12 to be rotated about its axis. By such pivotal motion the axis 11 of the 
eccentric arrives at 11', i.e., its clearance from the axis of the bar or 
rod material M is reduced and the clamping-cheek 2 therefore executes a 
lowering motion in the direction towards the feed path of the bar 
material. 
A second hydraulic operating-cylinder 16 is hinged at 18 to the machine 
frame. Its piston rod 19 is hinged to a plate 20 which at the same time is 
used as a stop limiting the position of the clamping-cheek 2 when it is 
swung into the cutting position, so that by acting upon the operating 
piston in the cylinder 16 the clamping-cheek 2 can be swung about the axis 
11 of the eccentric. The clamping-cheek 2 can thereby be swung from its 
clamping position which is shown in solid line in FIG. 1, into its cutting 
position shown in dash-dot line in FIG. 1, and back again. 
Since the clamping-cheeks 1, 2 for the reasons already stated are arranged 
close up against the stationary bending-mandrel 3, in the embodiment 
illustrated the bending-tools 3, 4 are formed to be retractable as a whole 
out of the plane of bend in the direction perpendicular to this plane in 
order not to impede the cutting process in direct proximity to the last 
point of bend. 
The stationary bending-mandrel 3 is for this reason mounted on a shaft 21 
onto which is keyed a pinion 22. This engages with a rack 23 which can be 
displaced by the piston rod of a hydraulic operating-cylinder 24, whereby 
the bending-tool 4 executes a swinging motion about the stationary 
bending-mandrel 3. 
The shaft 21 is by means of a coupling 25 connected rotatably but not 
displaceably to the piston rod 26 of an operating-cylinder 27 which can 
slide the bending-tools 3, 4 forwards into and retract them from the plane 
of bend. 
The admission of pressure medium to the hydraulic cylinders 16, 24 and 27 
is controlled by electrohydraulic spool-valves 28, 29, 30 of known 
construction. Each of these spool-valves exhibits two possible switch 
positions with each of which is associated the motion of the operating 
piston in the cylinder in a certain direction. 
The electrohydraulic spool-valve 31, however, which controls the admission 
of pressure medium to the operating-piston in the cylinder 13, shows a 
different construction. This slidevalve can be brought into three 
different switch positions. In the extreme righthand position of the 
spool, as shown in FIG. 1, the piston in the operating-cylinder is acted 
upon in the direction of a downwards motion. The piston in the 
operating-cylinder 13 is thereby acted upon by pressure medium on the face 
adjacent the piston rod, the axis 11 of the eccentric is brought into the 
position shown in FIG. 1 and held in it, and the clamping-cheek 2 is 
separated from the clamping-cheek 1 and releases the barlike material 
clamped between the clamping-cheeks 1, 2. 
If the spool 31 is shifted out of the position shown right over to the 
left, the piston in the operating cylinder will be acted upon by pressure 
medium in the direction of a upwards motion, that is, on the face opposite 
the piston rod. In that case the axis of the eccentric gets shifted in the 
direction towards 11' in FIG. 1 and the clamping-cheek 2 is pressed 
downwards with maximum force. 
In the mid-position of the spool 31 the operating piston in the cylinder 13 
gets acted upon by pressure medium on both sides at once. In this position 
a resultant upwards force is arranged to act on the piston, which causes a 
shift of the axis of the eccentric in the direction from 11 towards 11', 
this force being equal to the product of the liquid pressure and the area 
of cross-section of the piston rod 14. This force is therefore 
significantly smaller than the forces which in the two end positions of 
the spool 31 are exerted on the piston in the cylinder 13. 
By an electronic controller of the usual kind, which is not part of the 
invention and therefore does not need to be explained in further detail, 
the spool 31 is controlled in such a way that as long as the 
clamping-cheek 2 is in the clamping position shown in FIG. 1 the spool 31 
can only be brought into the position shown or into the mid-position. If 
the spool 31 is in its mid-position the clamping-cheek 2 is pressed 
against the strand of material with adequate force to clamp it firmly 
against twisting without however there being any danger of deformation of 
the material because of too high a pressure. 
Only if the clamping-cheek 2 is brought into the cutting position can the 
electrohydraulic spool be switched into its extreme lefthand position in 
order to bring into effect the full force corresponding with the product 
of the liquid pressure and the cross-section of the piston for severing 
the strand of material. 
Finally it may further be mentioned that the clamping-cheeks 1 and 2 
advantageously exhibit oblique wedge surfaces 32, 33 which face towards 
the bending-tools 3 and 4. These wedge surfaces serve to guide past the 
clamping-cheek barlike material being moved during the bending process in 
the direction of the clamping-cheeks, in order to prevent catching of the 
material on the clamping-cheeks.