US 3680339 A
Apparatus and method for synchronizing plural press brakes in sheet processing machines or presses having movable and fixed tables and a hydraulic control circuit associated therewith, wherein a mechanism is provided for operating the movable tables while keeping the same in close alignment, including a pilot mechanism which descends with a predetermined lag behind the descent of the movable tables, a bleed-off valve for each table, provided in the hydraulic circuit, and a mechanism for adjusting the hydraulic pressure for driving the movable tables.
Description (OCR text may contain errors)
United States Patent Hayakawa 1 Aug. 1, 1972  WORK START SYNCHRONIZER IN  References Cited PLURAL PRESS BRAKES COUPLING UNITED STATES PATENTS OPERATION 2,764,869 10/ 1956 Scherr ..91/171  Inventor: Masahiro Hayakawa, Sakaide, 3,393,635 7/1968 Richardson 100/269 R Japan 3,469,435 9/1969 Trautman ..100/258 R  Assignee: Amada Co., Limited, Kanagawa, primary Examiner chafles Lanham Japan Assistant Examiner-Gene P. Crosby 22 Filed: June 22 1970 Attorney-Cecily L. Frey  Appl. No.: 48,193  ABSTRACT Apparatus and method for synchronizing plural press  Foreign Application Priority Data brakes in sheet processing machines or presses having movable and fixed tables and a hydraulic control cir- June 25, 1969 Japan ..44/49679 cuit associated therewith, wherein a mechanism is vided for operating the movable tables while keeping  U.S. Cl ..72/28, 72/441, 100/258 A th same in close alignment, including a pilot  Int. Cl. ..B21j 9/20 mechanism which descends with a predetermined lag  Field of Search ..72/28, 404, 453, 441, 389, behind the descent of the movable tables, a bleed-off valve for each table, provided'in the hydraulic circuit, and a mechanism for adjusting the hydraulic pressure for driving the movable tables.
10 Claims, 2 Drawing Figures are coupled together, and subjected to working of long metal sheets, it is very difficult to perfectlysynchronize the movements of the movable tables, due. to differences in pump discharges, differences in the resistances between the movable tables and their guiding faces, or in the weights of these tables, even if the hydraulic mechanisms of the respective machines are identical and the actuation of the respective hydraulic change-over valves is carried out simultaneously.
Thus, a time lag is inevitably produced in the starting cause descent of the movable table 3L, thereby effecting bending work on a metal sheet placed between the movable table 3L and the fixed table 11L.
In order to return the movable table 3L to its original position after completion of the bending work, the valve 13L is manually switched to the opposite position, whereby the hydraulic fluid will push the piston 15L upwards from the bottom of the main cylinder 14L, and the fluid on the return side will pass through valve 13L, and finally arrive at the outlet 18L.
When two sets'of machines of the same type are used together, as in the illustrated embodiment of the present invention, it is found difficult to perfectly synchronize the movements of the movable tables 3L,
3R, as has been explained before. 1
of the pressing operation of the two machines, resulting Y in serious impairment of the quality and appearance of the products.
It is an object of the present invention to provide an apparatus and a method capable of overcoming the drawbacks of the known devices.
It is yet another object of the invention to provide an apparatus and a method for perfectly and precisely synchronizing the timing of the initiation of machining operations, more particularly in plural press brakes.
Other objects and advantages will become apparent As will be noted, the arrangement of the elemen positioned between the twosets of press brakes A, B is such that the pilot cylinder 8 is secured to the base:
block 1, and the valves 2L, 2R are secured to the leftand right-hand tables 3L, 3R, respectively, so that the size hydraulic change-over valve 13M, necessary for allowing a vertical motion of the pilot bar 7. The valve 13M is operated simultaneously with the valves 13L, 13R by manual operation, as the broken line shows in connection with these valves in FIG. 2, so as to effect a change-over from descent to ascent, or vice versa, of
the pistons in the respective cylinders.
The flow-adjusting valve 9 is pre-set so that when the same is fully opened the pilot bar 7 is moved pilot cylinder 8 mounted thereon, 2L and 2R are respectively leftand right-hand phase-difference sensing bleed-off valves, with bottom projections which will be explained later in more detail. 3L and 3R are moving tables on the left and right sides, 3L and 3'R are punches, 4 is a connecting punch, 5 a connecting die, 6 a coupled section of a foot switch, 7 a pilot bar, 9 a flow-adjusting valve, 10 a check valve.
11L and 11R are fixed tables, ll'L and ll'R dies, 12L and 12R flexible tubes, 13L, 13M and 13R (left, middle and right, respectively) hydraulic change-over valves. The middle valve 13M is of relatively small size. 14L and 14R are main cylinders, 15L, 15M and 15R pistons, 16L, 16M and 16R hydraulic regulators, 17L, 17M and 17R, as well as 18L, 18M and 18R, and finally 19L and 19R hydraulic outlets, P a pump, and M an electric motor or other conventional drive for driving the pump P. I
For a better understanding of the invention, the prior-art practice is first described, where each press brake is operated separately, with particular reference to the press brake A on the left-hand side of FIG. 2.
, When the hydraulic change-over valve 13L is manually made to descend, pressure of the pump P will actuate said valve 13L and force the piston 15L downward, substantially at the same speed as the movable tables 3L, 3R of the leftand right-hand presses A,
When the valves 2L, 2R contact the pilot bar 7,- the pressure fluid, which works to move down the pistons 15L, 15R in the respective main cylinders 14L, 14R, for operating respectively the leftand right-hand movable tables 3L, 3R, is urged to flow, past the valves 2L, 2R, to the respective outlets 19L, 19R.
There is also provided conventional means, such as a counterweight (not shown), to offset and make negligible the weight of the two movable tables.
The two press brakes are combined in proper alignment in such a manner that the pilot bar 7, the movable tables 3L, 3R and the fixed tables 11L, 11R are positioned in perfect parallel relation to each other and that the spaces or gaps between the pilot bar 7 and the bottom projections of the leftand right-hand bleed-off valves 2L, 2R are also of perfectly equal size. Also, the regulating valve 9 is slightly closed and adjusted so that during the descending stroke, under no load, the descent of the pilot bar 7 will slightly lag behind the descent of the movable tables 3L, 3R, as effected by the pistons 15L, 15R in the leftand right-hand main cylinders 14L, 14R.
During no-load descent under this condition, should the descent of, for example, the movable table 3L be faster than that of the movable table 3R, the bottom projection of the bleed-off valve 2L will first contact the pilot bar 7 to cause change-over of the fluid passage of this valve so that the fluid in the main cylinder 14L will pass through flexible tube 12L and flow from said valve to the outlet 19L, consequently causing a reduction of the descending velocity.
The same effecttakes place in the opposite sense, namely the movable table 3L or 3R which has a faster descending speed stops first, and since the descending speed of the pilot bar 7 is slower than that of the respective movable table, the latter, vwhile stopping alternately, starts its descent when the bottom projection of the respective bleed-off valve 2L or 2P leaves the pilot bar 7.
Thus, the leftand right-hand press brakes A, B keep their synchronization and the movable-tables 3L, 3R start their bending work simultaneously. Also, when the bending work is initiated, the required distances between the bleed-off valves 2L, 2R and the pilot bar 7 are maintained, and no leakageof hydraulic fluid occurs toward the outlets 19L, 19R, thus allowing the performance of the bending work with full capacity of the hydraulic pressure, as furnished by the pump P. Y
The ascending or return stroke, after completion of the bending work, produces no undesirable effects on It will be understood by those skilled in the art that the novel method according to the invention could'be carried out by the aid of mechanisms and means which are different from those shown and described herein, otherwise'known in the art, and thus the method is not considered to be limited tothe use of the exemplary apparatus embodiment as disclosed herein.
It should also be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the invention, and that it is intended to cover all changes and modifications of the example described which do not constitute departures from the spirit and scope of the invention.
' Whatl claim is:
1. An apparatus for synchronizing plural press brakes, associated each with a press which has a movable and a fixed table, and a hydraulic control circuit associated therewith, comprising, in combination, a mechanism for operating said movable tables while keeping the same in close alignment, a pilot mechanism which descends with a predetermined lag behind the descent of said movable tables, bleed-off valve means provided in said hydraulic circuit, and a mechanism for adjusting the hydraulic pressure for driving said movable tables.
tion of said ilot me hanism.
5. The syiich'roniz ing apparatus as defined in claim 1,
further comprising a punch associated with each movable table, a die associated with each fixed table, as well as interconnecting punch, die and foot-switch sections for operatively linking together said punches, said dies and said fixed tables, respectively.
6. The synchronizing apparatus as defined in claim 5, wherein said pilot mechanism includes a pilot cylinder, and a pilot bar secured to a moving portion of said pilot cylinder, and wherein said bleed-off valve means are adapted to. be acted upon by respective ends of said pilot bar. j Y
7. The synchronizing apparatus as defined in claim 6, wherein said pilot mechanism further includes means for retaining said pilot bar in substantially parallel relation to said punches and said dies.
8. A method for synchronizing plural press brakes, associated each with a press which has a movable and a fixed table, and a hydraulic control circuit associated therewith, including bleed-off valve means, as well as a pilot mechanism for said movable tables, and means for actuating the descent of the pilot mechanism comprising the steps of operating said movable tables while keeping them in closely aligned relation, in such a manner that the descent of said pilot mechanism lags behind the descent of said movable tables, and adjusting the hydraulic pressure for driving said movable tables when said valve means engage with said pilot mechanism.
9. The synchronizing method as defined in claim 8, wherein each press has a punch and a die respectively associated with its movable and fixed tables, further comprising the step of operatively-linking said punches, said dies and. said fixed tables by interconnecting punch, die and foot-switch sections.
10. The synchronizing method as defined in claim 9,
I further comprising the step of retaining at least a portion of said pilot mechanism in substantially parallel relation to said punches and said dies.