|Publication number||US3812694 A|
|Publication date||28 May 1974|
|Filing date||30 Nov 1971|
|Priority date||30 Nov 1970|
|Also published as||DE2058793A1, DE2058793C2|
|Publication number||US 3812694 A, US 3812694A, US-A-3812694, US3812694 A, US3812694A|
|Original Assignee||P Peddinghaus|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (10), Referenced by (10), Classifications (11)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 1191 Peddinghaus 1 May 28, 1974 i 1 BENDlNG MACHINE FOR METAL RODS 22 Filed: Nov. 30, 1971  Appl.No.:203,340
 Foreign Application Priority Data Nov. 30, 1970 Germany 2058793  US. Cl 72/21, .72/7, 72/D1G. 22, 72/702  Int. Cl B2ld 7/024  Field of Search 72/7, 21, 8, 9, 10, ll,
72/12, DIG. 22, 702, 22.
 References Cited I UNITED STATES PATENTS 3,145,756 8/1964 Hill 72/7 3,156,287 11/1964 Munro 72/8 3,352,136 11/1967 Clarke 72/9 3,393,543 7/l968 Van Gelder 72/26 3,407,850 10/1968 Kelm 72/702 3,459,018 8/1969 Miller 72/7 3,512,383 5/1970 Arnold et al 72/22 3,661,002 5/1972 Peddinghaus, Jr.. 72/21 3,670,541 6/1972 Peddinghaus 72/8 FOREIGN PATENTS OR APPLICATIONS 1,244,529 7/1967 Germany 72/149 Primary ExaminerCharles W. Lanham Assistant Examiner-M. .l. Keenan Attorney, Agent, or Firm-Holman & Stern 57 ABSTRACT A bending machine for bending metal rods having a rotatable bending plate which carries a centrally disposed bending tool and at least one eccentric bending tool, means being provided for continuing angular movement of the rotatable bending plate beyond a nominal angular position in order to compensate for spring-back of a metal rod after a bend has been effected, there being impulse transmitting means actuable on rotation of the bending plate, means for counting impulses transmitted by said impulse transmitting means and means for comparing such transmitted impulses with a number of impulses pre-set in said counting means. The rotatable bending plate continues beyond th'e nominal bending angle by the provi-' sion of delay means which delay' by a pre-selected variable periodv the moment at rwhich the number of transmitted impulses correspondsto the number of impulses pre-set in the counting means. The period of said variable delay is proportional to the value of the nominal bending angle, the value of the ratio of the diameter of the centrally disposed bending tool to the diameter of the rod being bent and a factor, dependent upon the. hardness of the rod, lying between 0.004 and 0.008.
' 6 Claims, 3 DrawingFigures PATENTEDIAY28 I914 3.812.694
SHEEI 1 (IF 2 4IVNV ENTOS BY A/ PATENTEDHAY 28 I974 SHEEI 2 0F 2 FIG. 3
BACKGROUND OF THE INVENTION The invention relates to a bending machine for metal rods, such as steel reinforcing rods, the machine having a bending plate which carries a central bending tool and at least one eccentric bending tool, and being arranged to effect bends in both angular directions, with the bending plate being automatically returned to a starting position after it has turned through a required bending angle.
PRIOR TECHNIQUES In bending machines of this type, a bent rod will spring back elastically a limited amount after a bend has been made. Since, after a bend which was set at a specific nominal bending angle has been made, the angle of thebend would be too'small because of this spring-back. certain adjustments must be made, using test bends, until the required bend is achieved. It is.
known that cams for instance can be used to make such adjustments, with these cams beinginserted in various holes on the periphery of a disc which rotates with the bending plate. It has also been suggested that the bending operation can be set to continue automatically after a preselected bending angle has been achieved, so that the spring-back already mentioned is compensated for. It has further been suggested that a standing value indicator can be used, by means of which the drive remains switched on, after a predetermined-bending angle has been achieved, for a further time which is the same as the idlingtime,-namely the time taken by the bending plate initially until its bending tools are loaded and the initial resilience of the rod to be bent has been taken up. Here too, however, a test bend must first of all be made and measured in order for the standing value indicator to be set, said indicator comprising, for example, a potentiometer which can vary the timeconstants of an RC network.
OBJECTS AND SUMMARY OF THE INVENTION In distinction to the above expedients, the object of this invention is to provide an improved bending machine of the type described in the introduction so'that such test bends or measuring operations are not needed except for a single test bar bend. I
In accordance with the invention, there is provided a bending machine for bending metal rods having a rotatable bending platewhich carries a centrally disposed bending tool and at least one eccentric bending tool, a series of electrical contact means rotatable with said bending plate and angularly spaced at positions corresponding to the nominal value of various required bends, impulse transmitting means actuable by said contact means on rotationthereof, a counter for recording impulses received from said impulse transmitting means and means for pre-setting in said counter a pre-determined number of impulses corresponding to any given required bending angleand means for reversing the angular movement'of said bending'platesoas to return it to a zero position at a moment when the number of impulses transmitted by said impulse transmitting means corresponds to the number of impulses pre-set in said counter, characterized in that, for any given nominal bending angle, means are provided for delaying, by a preselected variable period, the moment at which the number of impulses transmitted by said impulse transmitting means corresponds to the number of impulses pre-set in said counter, thereby permitting the bending plate to rotate through an angle greater than said nominal bending angle, the period of said delay being proportional to the value of the nominal bending angle, the value of the ratio of the diameter of the centrally disposed bending tool to the diameter of the rod being bent and a factor, dependent upon the hardness of said rod, lying between 0.004 and 0.008.
With an average strength of reinforcing steel rods a constant proportionality factor of about 0.0063 can be used.
It is therefore particularly possible, in accordance with the invention, to do away with test bends or measuring operations during the bending process. In practice the value of the ratio bending tool diameter/rod diameter only has to be adjusted if one changes over to other diameters. Thetool which is fitted centrally on the bending plate is considered to be the bending tool in the sense of the invention. Since this tool in particular is frequently left unchanged, only the diameter of the rod needs to be considered, in most cases, in order to compensate for the spring-back resilience in the manner described in the invention. Since said rod diameter is always known this simplifies considerably the way in which the machine works.
The electrical contact means are arranged for convenience on adisc which rotates with the bending plate, saidcontact means actuating an impulse transmitter of which the impulses are recorded .by a switch meter or counter which can be adjusted by an adjusting switch on which the bending angles are marked, to a number of impulses corresponding to the pre-selectedbending angle. Said contact means may comprise a' single contact at each of a plurality of positions corresponding to the required nominal bending angles and in this case the contacts'may be adjusted by a common adjusting device, on which then only the ratio of the bending tool diameter/rod diameter has still to-be adjusted. Due
to the adjustment of this ratio all contacts on the disc then alter by an amount which increases proportionally as the nominal bending angle increases.-ln another embodiment it is advantageous to have several contacts at I each of the nominal bending angle positions and in this case the number of impulses which are to be pre-set in the counter can be varied as required so that for any given nominal bending angle a variable number of said contacts has to actuate the impulse transmitting means before parity is achieved with the aforesaid pre-set number of impulses. v
In addition a further method which can be used is for the electrical contact means to be delayed electrically, for instance by means of RC networks.
BRIEF DESCRIPTION OF THE DRAWINGS The invention .will now be more particularly de-.
FIG. 2 is a fragmentary plan view showing means whereby the position of an electrical contact on the ad justingdisc can be varied, and
FIG. 3 is a schematic view showing an alternative form of adjusting disc and means, associated with said disc, for setting various bending angles.
DETAILED DESCRIPTION OF THE I EMBODIMENTS Referring to FIG. 1, the bending machine shown therein has a bending plate 1 which carries a central bending tool 2 and an eccentric bending tool 3. Between said bending tools, a rod 4 which is to be bent is placed, said rod being supported in a known way is driven with the bending plate by any suitable andconventional drive means (not shown) such as an electric motor, with said disc 9 supporting in addition to a zero contact 10 at least th'reefurther contacts (not shown) atpositions ll, "12 and 13 corresponding to bending angles 45, 90 and 180.The contacts are arranged to actuate animpulse transmitting means including contacts indicated by reference numeral 14 the impulses from whichare counted-in a manner which is not the subject of the present invention, whereby after a specific number'of impulses, the aforesaid motor or drive means will be stopped and reversed to return the bending plate to its initial position.
In FIG. 1, the contacts 11 and 12 are shown on the righthand side of the disc 9 as seen in the drawing. It will be appreciated, however, that in practice similar contacts will be provided on the left-hand side of the disc 9 since, of course, it may be required to drive the bending plate 1,-togetherwith the disc 9, in a clockwise direction as well as an anti-clockwise direction depending on what kind of bend is required. All suchcontacts are arranged, however, so that on passing the contacts 14(whichare connected in an impulse transmitting circuit) an impulse will be transmitted to a counter (not shown) which can be of any known form.
Also, in accordance "with known practice, a preselected number of impulse's'can be set in such 'a counter so that the'number of such pre-set impulses is compared with the number of impulses received from the impulse transmitting circuit of which the contacts 14 form apart. When these two numbers of impulses are equal-then the aforesaid counter is arranged so that a signal is'applied to the drive motor of the bending plate to cause'such drive motor to be reversed in order to return the bending plate to its initial position.
FIG. 2 shows a part of an adjusting disc 9 in which two successive contacts indicated by reference numer als I5 and 16 can be seen. These contactors can slide along arcuate slits l7 and 18, for which purpose a forked end 19 of a lever ZO-engageseach contact, with said fork being slit in a radial direction. Each lever 20 has a fulcrum 21 which is connected to the adjusting disc 9, whereby the positions of the fulcrum points 21,
22 in successive levers is-such that they are disposed at increasing radial distances fromthe associated slits 17, 18 in proportion to their angular distance from each. other. A further but smaller. disc 23 is mounted concen-. trically onthe adjusting disc 9, with said disc 23 being constructed with slotted brackets or slits 24 and 25, into which the inner ends of 'said levers project. In addition, the disc 23 is provided with a scale 26 which can be set against a mark 27 on the disc 9, the scale being marked with a plurality of various values for the ratio of bending tool diameter to rod diameter, i.e., the distance 7 divided by the distance 8. Thus, if the disc 23 is moved in the direction of the arrow 28 the contactors l5, 16 will be moved by said leversso that there is a proportional increase, in the forward direction 29 of movement of the adjusting disc 9, in the distances by which said contactors are advanced in their arcuate slits 17 and 18.
With the apparatus shown in FIG. 2 it will be appreciated that the only adjustment which will normally be required is that involving angular movement of the disc 23 in order to compensate, if necessary, for a variation in the value of the ratio of the bending tool diameter to the rod diameter, it being understood that the different positions of the fulcrum points 21, 22 will also compensate for the different nominal bending angles. The apparatus is, however, designed so that the adjustment made by the disc'23. will also include a further factor,
namely a factor which is dependent upon the hardness of the rod being bent and which lies within the range of 0.004 and 0.008, a preferred value of such factor being 0.0063. l
It was determined that the actual bending angle which has to be imparted depends firstly on the nominal value or the required final value of the bending an-.
. pirical and is very easily determined by experiment for any particular grade of steel. One can take a test bar and bend it experimentally so as to finish up with acertain nominal bending angle, the total angle through which the bar is bent being greater, of course, than the nominal or final value by the amount of the spring-back angle. The spring-back angle can thus be measured experimentally in this one test bend and if this angle is then divided by the product of the nominal value of the bending angle and the ratio of the diameters of the bending tool and the bar, the above-stated factor will be determined for that particular grade of steel. It is pointed out that the above-mentioned factor is purely empirical, can easily be determined by one experimental bend, and is a constantfor any particular grade of steel.
Ordinarily, the hardness of rods being bent bythe bending machine will not alter significantly. If, however, the hardness does vary to an extent which makes it necessary to vary the above-mentioned factor within the range stated, then the radial positions of said fulcrum points are altered and this can be effected by arranging that said fulcrum points 21 and 22 are themselves mounted in radially extending slits so that their radial positions on the disc 9 can be varied.
. In an alternative embodiment shown in FIG. 3 an adjusting disc 9 shown therein has further contacts 15',
16' closely adjacent to contactors 15, 16 respectively. Thus, at each of a plurality of positions corresponding respectively to the nominal bending angles, there is a group of contacts such as and 15' or 16 and 16. An impulse transmitting means having contacts similar to the contacts indicated diagrammatically by reference 14 in FIG. 1, is also actuated by these contacts 15 and 15 or 16 and 16'. The impulses from said transmitting means are then supplied to an impulse counter 30 which is set to a specific pre-determined number of impulses by means of an adjusting switch 31, and which then controls the electric motor'driving the bending plate through an electric conduit 32 connected thereto. For setting the adjusting switch 31, there is provided an adjusting disc 33 which has various angle markings 34. A shaft 35 and a shaft 36 are disposed between the adjusting disc 33 and the adjusting switch 31 and are connected together by a gear 37 which is infinitely variable in the range of l l to l L1. This gear can, for instance, as shown be made up of two frusto-conical parts 38 and 39 which are connected together by a belt 40 which can be moved in an axial direction. An adjusting fork 41 is provided for adjusting the position of the belt 40, with said fork having a part movable in a slot 42. There is also an indicator 43 which points to a scale 44 on which the various values of the ratio of tool diameter/rod diameter (seven-eighths) as before can be adjusted. In this way a specific bending angle can be set by adjusting disc 33. However, as a result of the aforesaid gear 37 and adjusting switch 31,-a greater number of impulses will be set on the switch meter 30 than corresponds to the nominal angle of rotation of the bending plate. In order to stop and reverse the drive of the bending plate several additional impulse transmissions must be given and these are triggered off by the contactors 15 or 16' so that in this way the spring-back angles can be compensated for.
With the embodiment shown in FIG. 3, it is thus possible to vary the number of impulses pre-set in the counter 30 by means which compensate both for the nominal bending angle and also for the value of the ratio of the bending tool diameter to the rod diameter. As above-described the last-mentioned ratio is varied by sliding the fork 41 to the right or left without rotation, the position of the fork being fixed by means of some suitable clamp operating in the slot 42. a
The above-mentioned ratios by which the gear 37 can be varied, namely avariation within the range of l l to l 1.1, will, it will be appreciated, provide for a variation of up to 10 percent so that, for example, when a nominal bending angle of 90 is required, an additional bending angle to compensate for the spring-back effect of up to 9 can be set and in practice such an addition is found to be more than sufficient.
As is the case with the embodiment shown in FIG. 2, the aforementioned factor, dependent upon the hardness of the rod being bent, will normally remain constant at the preferred value of 0.0063. If, however, it is required to vary this factor because of varying hardness of the rod being bent, then suitable compensation can be effected by moving the two parts 38 and 39 of the gear 37 axially relative to each other, with means being provided to ensure that the tension of the belt 40 is correctly adjusted. As an alternative to this, the aforementioned factor, dependent upon the hardness of the rod, can also be adjusted by arranging so that the fork 41 is, in addition to being movable to right or left along the 6 slot 42, is also pivotable, for example, about apivot which connects said fork 41 to a slide which moves in said slot 42. In this case, a dial can be mounted on such pivot and on this dial would be marked various values tor can easily be set. In any event, it will be appreciated that with the embodiment shown in FIG. 3, the number of impulses pre-set in the counter 30 can be varied in order to delay the moment when impulses received by operation of the contacts 15, 15', 16 and 16 equal the number of pre-set impulses in order that the bending plate drive motor can be reversed. On the other hand, with the embodiment shown in FIG. 2, the number of pre-set impulses will remain the same but the appropriate delay to compensate for spring-back is achieved by altering the positions of the contacts themselves on the disc 9.
1. A bending machine for bending metal rods having a rotatable bending plate which carries a centrally disposed bending'tool and at least one eccentric tool,'a-series of electrical contact means rotatable with said bending plate and angularly spaced atpositions corresponding to the nominal value of various required bends, impulse transmitting means actuable by said contact means on rotation thereof, a counter for-recording impulses received from said impulse transmitting means and means for pre-setting, in said counter, a pre-determined number of impulses corresponding to any given required bending angleand means for reversing the angular movement of said bending plate so as to return it to a zero position at a moment when the number of impulses transmitted by said impulse transmitting means corresponds to the number of impulses pre-set in said counter, characterized in that, for any given nominal bending angle, means are provided for delaying, by a preselected variable period, the moment at which the number of impulses transmitted by said impulse transmitting means corresponds to the number of impulses pre-set in said counter, thereby permitting the bending plate to rotate through an angle greater than said nominal bending angle, the period of said delay being proportional .to the value of the nominal bending angle, and the value of the ratio of the diameter of the centrally disposed bending tool to the diameter of the rod being bent.
2. The bending machine as claimed in claim 1 wherein said electrical contact means comprises a single contact at each of a plurality of angularly spaced positions corresponding to said nominal bending angles, the contacts being mounted on a disc rotatable with the bending plate and wherein said delaying means comprises means for angularly retarding said contacts on said disc.
3. The bending machine as claimed in claim 2 wherein each contact is mounted for movement in an arcuate slot formed in said disc and is engageable by one end of a radially extending lever pivotally connected intermediate its ends on said disc, the other ends of said levers being engageable by a rotatable adjusting member and the pivots of said levers being disposed at varying distances from the ends thereof engageable with said contacts whereby rotation of said adjusting member will simultaneously pivot said levers so that the contacts will be moved in their arcuate slots sponding' to a plurality of nominal bending angles and wherein said delaying means comprises means for increasing, by a pre-selected, variable amount, the num ber of impulses pre-set in said counter'for any required bending angle.
6. The bending machine as claimed in claim 5 wherein said means for increasing the number of impulses pre-set in said counter comprises a rotatable setting member and an adjusting switch which are interconnected by means of a variable-ratio gear. Y
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|U.S. Classification||72/14.1, 72/702|
|International Classification||B21F1/00, B21D7/12, B21D11/12, B21D7/02|
|Cooperative Classification||Y10S72/702, B21D11/12, B21D7/12|
|European Classification||B21D11/12, B21D7/12|