Control unit of the bidirectional traverse of the cutting members in a machine to cut material in sheet form

Abstract: Control unit to obtain bidirectional traverse of the cutting members in a machine for the parting and/or cutting of a mate­ rial in sheet, preferably of paper type, to obtain reciprocal positioning of the knife and counterknife required for cut­ ting. The control unit according to the invention comprises pneu­ matically drivable means, which, once activated, determine the coupling of the means of support of the knife and counter­ knife to a worm screw in rotation which causes horizontal bi­ directional traverse of said means of support.

Description: The present invention refers to a control unit of the bidirectional traverse of the cutting members of a machine to cut material in sheet. More in particular, the present invention refers to a control unit, associable to the knife and counterknife of a machine for the cutting of material in sheet, preferably paper, which makes it possible to make the reciprocal positioning of said knife and counterknife so that they can make a correct cut of the abovementioned material. In the machines designed to cut material in sheet, preferably paper, knives and counterknives cooperating with pairs are generally used, whose reciprocal position makes it possible to make the cut of the abovementioned material along prefixed lines. The problem in this type of machines was to construct control units suitable to carry out a correct movement of the knives and counterknives, to position them at a reciprocal distance which permits the material to be cut precisely and perfectly without burrs. To achieve this, positioning of the knives and counterknives was carried out in various ways. A first known way of positioning the knives and counterknives consists in providing each of the cutting members with autonomous means of control of their movements. This solution, even if technically valid, is, in practice, extremely complicated and expensive as it is difficult to organize the high number of supply cables, and due to the high number of motors associated to each control unit. A further known system to position the cutting members consists of means of friction placed between said cutting members and the feed means. Once again, however, a complicated, expensive, technically unsatisfactory structure is obtained. In fact, the friction coupling is not always reliable due, in particular, to the wear deriving from numerous operations required in time. Furthermore, the plurality of frictions necessary for each machine need complex control members, generally of electronic type, whose costs affects that of the machine. To solve the above problems, a device has been proposed for the selective or simultaneous traverse of the positioning of the cutting members, which eliminates the complexity of the traditional machines and the consequent excessive cost of same, and their precarious reliability in the positioning of the various control units. This known device essentially comprises substantially bar-formed elements placed in rotation which are coupled to means associated to the knife and counterknife, which transform the movement of rotation into a movement of traverse of the knife and/or counterknife along the respective supporting beams. Said known means to transform the rotating movement of the bar-formed elements into movement of traverse in each cutting member, comprise: a series of connecting means, corresponding to the number of cutting members, keyed and torsionally fixed on each bar-formed element; a substantially cylindrical structure fixed to each cutting member, in which a small shaft is inserted, equipped at one end with a pinion engaged in a rack obtained on the supporting and slip beam of the cutting members, and two bushes inserted along the axis of said small shaft, one of them being axially stationary and free to rotate around said small shaft and equipped with means engaged at right angle with one of said connecting means, and the other torsionally fixed bush being axially mobile with respect to the first bush and moving axially, determining a torsional tie or clearance between said two bushes. Said device for the selective or simultaneous traverse of the positioning of the cutting members is object of a previous patent application, in the name of the same applicant, not yet public. Said device was particularly reliable, simple to operate and suitable to make a precise, correct positioning of the knives with respect to the counterknives. US-A-4320677 discloses an apparatus according to the preamble of claim 1. In this apparatus the locking means is formed by two clutches. The object of the present invention is to improve the control unit of bidirectional traverse of the cutting members. According to the present invention, this and other objects which will result from the following description are obtained by means of a control unit according to claim 1. Preferably, the stop means comprise, on each side of the nut screw, as essentially cyclindrical body which is engaged with said nut screw to control the stop in rotations. Alternatively, said stop means can be a pneumatic piston contrasted by a spring and provided at the end with a stop tooth which is engaged in a corresponding hollow of the nut or female screw. The constructive and operating characteristics of the control unit of the present invention can be better understood from the following detailed description in which reference is made to the attached drawings which show a preferred, illustrative but unbinding implementation of the present invention, and in which: fig. 1 shows the schematic from view of a machine for the cutting and/or parting of material in sheet, provided with the control units object of the present invention; fig. 2 shows the schematic view of a control unit according to section II - II of fig. 1 in the activation condition in which this unit determines the movement of the knife or counterknife; fig. 3 shows the similar schematic view of fig. 2, with the same control unit in deactivation position in which the knife or counterknife are stationary; fig. 4 shows the schematic view of the control unit according to section IV - IV of fig. 2; fig. 5 shows the schematic view of a constructive variant of the control unit, always seen according to a section similar to the section II - II of fig. 1. Reference will first be made to fig. 1 to describe in greater detail, as a whole, the structure of the machine equipped with the control units according to the invention. With reference to the above figure, the machine for the parting and/or cutting of material in sheet comprises a pair of screws (10), parallel to each other, one of them placed in the upper part of the machine, the second in the lower. To each of the screws (10) is associated a plurality of control units, each indicated in the complex with (12), which, on each of the screws (10), are in equal number to the knife-counterknife assembles to be moved. The screws (10) and operative members, which will be mentioned later, are supported by a support frame of the machine not shown. Cog-wheels (14) are keyed on the superimposed ends of the screws (10), which are interconnected by a chain (16) which makes it possible to transmit movement in synchronous way from the end of the upper screw (10) connected to a control motor (18) at the end of the lower screw (10). In this way the screws (10) will rotate in synchronism the one with respect to the other. To each of the screws (10) is associated a slip beam (20) which extends parallelly to the relative worm screw (10). Along the slip beam (20) slide the means of support of the knives (24) and counterknives (24a) of the machine. Said means of support are shown in more detail in figures 2 to 4. Each means of support comprises a compound bracket, indicated as a whole with (22), which is fixed from one side to the control unit (12), while, from the other side, it supports in known way the knife (24). Figures 2 to 4 show only the knife (24), the means of support of the counterknife (24a) have an essentially identical structure and the counterknife is shaped in substantially similar manner to the knife (24), i.e. it is also of essentially circular shape. The shape of the compound bracket (22) and the movement of the knife (24) with respect to the counterknife to make the cut are not described in detail as they are made in traditional way. The compound bracket (22) is equipped, on the side opposite that where the knife (24) is positioned, with small rollers (26) which can translate on the slip beams (20). The control unit (12) according to the invention comprises a hollow body (30) inserted in the screw (10) and means of pneumatic or hydraulic type placed in the hollow of said body to control the movement of the means of support (22) to which the knife (24) and counterknife (24a) are connected. The hollow of the hollow body (30) has preferably the shape of a cylindrical chamber (28). The above mentioned pneumatic mean of each control unit (12), placed inside said cylindrical chamber (28) comprise a pair of essentially cylindrical bodies (32) placed on the opposite sides of the screw (10). Said cylindrical bodies (32) have the diameter at right angle to that of the screw (10), slide sealed in the chamber (28) by means of seal gaskets (34) and are shaped substantially like a head of a pneumatic piston without shank. Each of the cylindrical bodies (32) has the facing surface shaped to be engaged with a female screw, in particular a female screw with recycling of balls (36) in which the screw (10) can rotate. In the condition shown in fig. 2, the cylindrical elements (32) are engaged with the female screw (36), locking its rotations; in this condition, as the screw (10) is always in rotation, the control unit (12) associated to this segment of female screw will consequently be made translate. The control unit (12) is driven by compressed air coming from a suitable feed source (not illustrated) which reaches said unit in the direction of the arrow F through a feed duct (38). The compressed air is inserted in the chamber (28) through an inlet duct (40) to the first of the cyclindrical bodies (32), and, through a shunted duct (42) obtained in the body (30) of the control unit (12), to the second of said cylindrical bodies (32). In this way, through the insertion of compressed air in the chamber (28), the two cylindrical bodies (32) will be brought nearer to each other, so that they are engaged with the female screw (36) to lock their rotations and control its movement along the screw (10). Fig. 3 shows the control unit (12) in deactivated condition, in which the compressed air is no longer sent to the chamber (28) of the control unit (12). In this condition the cylindrical bodies (32) are released from the female screw (36), which, supported at opposite ends by bearings (35) placed in the body (30) can rotate with the screw (10) without causing displacement of the knives (24) or counterknives (24a). With particular reference to fig. 1, the various control units (12) are fed by a pneumatic circuit comprising a feed duct (46) for each of the screws (10) on which is derived a plurality of feed ducts (38), on each of which an on-off valve (44) is inserted. Figure 5 illustrates a constructive variant of the control unit (12). In this form of construction, the control unit (12) comprises a suitably shaped piston which slides in the chamber of the hollow body (30). The chamber presents an upper and lower part (53) of smaller diameter and a central part (48) of wider diameter. In the portion (48) with wider diameter, compressed air is inserted through the underlying feed duct (38) and inlet duct of the compressed air (40). The piston comprises an intermediate portion (50) of larger diameter which slides with seal in the central part (48) of the chamber, and a portion (51, 56) of smaller diameter which slides with seal inside the chamber (53) of the body of the control unit (12). The portion with larger diameter (50) cooperates with a spring (54) wound round the body of the shank (52) of the piston and is engaged, at one end, with the portion with larger diameter (50) of the piston, and,with the other end, with the upper inside surface of the chamber. The free end of the portion (56) with smaller diameter is equipped with a stop tooth (58) suitable for engagement in a corresponding hollow (60) provided traversally on the section of the female screw (36). This form of alternative construction operates as follows. When compressed air is not fed to the control unit (12), through the ducts (38) and (40), as shown in fig. 5, the mobile piston of said unit is brought, by action of the spring (54), to the position shown in said fig. 5 in which the tooth (58) is engaged in the hollow (60) of the female screw (36), locking its rotations. In this operative phase, the screw (10) being always in rotation (10), the nut screw (36) will cause a translation of the knife (24) or counterknife (24a) associated to it. When compressed air is inserted in the chamber of larger diameter (48), the mobile piston of the control unit (12) is lifted from the previous position so that its stop tooth (58) will be released from the hollow (60) of the female screw (36). The latter does not therefore control the translations of the knife (24) or associated counterknife (24a). The means of drive described above of the control unit (12) which have been illustrated of pneumatic type could also be, according to a further final variant, of electromagnetic type. It would be sufficient for this purpose to substitute the means described above with a pair of magnets, the first integral to the cylindrical body (32) of the first form of implementation of figures 2-4 or to the cylindrical body (50,51) of the final variant of figure 5, while the second could be integral to the second cylindrical body (32) of the first form of implementation and to the portion (56) of the mobile piston of the second form of implementation.

Claims: An apparatus for cutting a material in sheet form by means of a plurality of pairs of knives (24) and counterknives (24a), which comprises one upper screw and a lower screw (10), arranged parallel to each other and spaced therebetween, a motor means (18) for rotating said upper and lower screws (10), means (14,16) for transmitting motion from one end of the upper screw to the lower screw (10) whereby said screws rotate synchronously, a slip beam (20) associated to each screw (10) and parallel thereto, control units (12) associated to each said screw (10) in number equal to the knives (24) and counterknives (24a), support means (22) for supporting said knives (24) and counterknives (24a) sliding on each said slip beam (20), said support means (22) comprising a bracket having a first end fixed to each of said control unit (12) and a second end fixed to each knife (24) or counterknife (24a), said control units (12) comprise a rotating nut screw or female screw (36), in which said screw rotates, and stop means for locking said female screw (36) causing the motion of said control unit (12) and, therefore, of the support means (22) fixed thereto, and having means of hydraulic or pneumatic type for locking the female screw characterized in that said stop means comprising a hollow body (30), having a cylindrical chamber (28), through which said upper or lower screw (10) runs, and said means of hydraulic or pneumatic type (32,50) for locking the female screw (36) being arranged within the cylindrical chamber (28) on the side of the female screw (36). The apparatus for cutting a material in sheet form according to claim 1, characterized in that the means of hydraulic or pneumatic type for locking the female screw (36) comprises a pair of cylindrical bodies (32) placed on the opposite sides of the female screw (36) and sealingly slidable in the cylindrical chamber (28), each of said cylindrical bodies (32) having the facing surface shaped to engage with the female screw (36); and ducts (40,42) for feeding compressed air in the opposite parts of the cylindrical chamber (28) for moving the cylindrical bodies (32). The apparatus for cutting a material in sheet form according to claim 2, characterized in that the female screw (36) is supported at its opposite ends by bearings (35). The apparatus for cutting a material in sheet form according to claim 1, characterized in that the control unit (12) comprises: a hollow body (30) having a cylindrical chamber (28), the diameter of which is smaller in the upper and lower (53) parts and wider in the central part (48); an inlet duct (40) of compressed air in the wider part (48) of the cylindrical chamber; a piston consisting of: an intermediate portion (50) of larger diameter sealingly sliding in the wider part (48) of the cylindrical chamber, an upper portion (52) sliding in the upper part of the cylindrical chamber, and a lower portions (51,56) sealingly sleading in the lower part (53) of the cylindrical chamber; the free end of the lower portion (56) being equipped with a stop tooth 58). a spring (54) wound around the upper portion (52) of the piston and placed between the upper surface of the larger portion (50) of the piston and the upper inside wall of the cylindrical chamber; and a hollow (60) provided on the surface of the female screw (36) suitable for engaging with the stop tooth (58).-

Inventors: CAVAGNA ELIO, CAVAGNA, ELIO
Applicants: CAVAGNA ELIO, CAVAGNA, ELIO
Application year: 1988
Main classification: B26D7
IPC codes: B26D7, B26D1, B23D19