Field of The Invention

[0001] The present invention generally finds application in the field of tanning equipment and particularly relates to an improves staking machine for flexible sheet products.

Background art

[0002] Machines known as staking machines have been long known to be used in tanning factories for softening and stretching flexible sheet products such as industrial hides and similar products having opposite sides, i.e. a grain side and a flesh side.

[0003] These machines are used in the steps after tanning and/or drying to restore the natural softness of leather, as well as increase its size, i.e. the useful leather area.

[0004] Generally, these machines comprise motorized feeding means for feeding products in a predetermined direction, which consist, for instance, of a pair of mutually facing belts, with sheet products to be staked interposed therebetween.

[0005] These machines further comprise one or more pairs of mutually facing beating plates parallel to the longitudinal direction. The plates are reciprocated to move toward and away from each other substantially perpendicular to the product feeding plane.

[0006] In addition, each plate has tools or pegs, which are adapted to interact with corresponding matingly shaped cavities or recesses on the opposite plate.

[0007] EP2049694, by the proprietor hereof, discloses a perching machine comprising at least one stationary plate and a movable plate, which are associated with means for adjusting the mutual distance between the two plates.

[0008] These adjustment means can adjust the staking pressure on opposite sides of the hides and, as a result, product finishing.

[0009] While this machine satisfactorily fulfills its intended tasks, it is still susceptible to improvement, namely in view of increasing effectiveness and throughput of the machine.

[0010] The useful leather area and softness of flexible sheet products are directly dependent on the feeding speed through the machine and the number of beats/minute of the beating plates.

[0011] Nevertheless, the feeding speed of the products may be adjusted within a restricted range, which is directly associated with the product feeding speed in the line, and is proportional to throughput.

[0012] In order to at least partially obviate this drawback, machines have been developed that can adjust the number of beats per minute of the reciprocating motion of the movable plate.

[0013] The number of beats is generally changed by adjusting the speed ratio between the motor to the drive shaft that imparts motion to the movable plate.

[0014] Nevertheless, due to the considerable mass of the beating plates, such adjustment can be only be carried out discretely and with the machine shut down, which increases the processing times and reduces the working coefficient.

[0015] A further drawback of this arrangement is that it requires manual adjustment by an operator, which increases the complexity and labor- intensiveness of the adjustment steps.

[0016] Another drawback of this arrangement is that, for speed ratio adjustment, the operator shall manually access the mechanical moving parts, that are usually placed below the feeding means in hardly reachable positions.

[0017] EP0829543 and CN104746352 disclose staking machines for softening and stretching flexible sheet products as defined in the preamble of claim 1.

Technical Problem

[0018] In the light of the prior art, the technical problem addressed by the present invention is to provide a staking machine that affords effective and immediate adjustment of the number of beats, to promptly adapt the machine to the various types of products to be treated and the characteristics of the desired products.

Disclosure of the invention

[0019] The object of the present invention is to obviate the above drawback, by providing an improved staking machine for softening and stretching flexible sheet products that is highly efficient and relatively cost- effective.

[0020] A particular object of the present invention is to provide an improved staking machine of the aforementioned type that can continuously adjust the number of beats/minute of the movable plate or movable plates.

[0021] A further object of the present invention is to provide an improved staking machine as described hereinbefore that can reduce power consumption at startup.

[0022] A further object of the present invention is to provide an improved staking machine as described hereinbefore, that can considerably reduce the overall flexible sheet product processing times.

[0023] Another object of the present invention is to provide a machine as described hereinbefore that can easily reduce the number of beats of the plates within a wide adjustment range.

[0024] A further object of the present invention is to provide a machine as described hereinbefore that is highly flexible and allows adjustment of the number of beats according to the sheet product feeding speed.

[0025] These and other objects, as more clearly explained hereinafter, are fulfilled by an improved staking machine as defined in claim 1 , for softening and stretching flexible sheet products, such as industrial hides and the like having opposite sides, which machine comprises motorized feeding means for conveying the products in a predetermined longitudinal direction, at least one pair of mutually facing beating plates substantially parallel to the feeding means and acting on the opposite faces of the products, where one of the plates is stationary and the other is movable.

[0026] The machine further comprises motor means associated with the movable plate of each pair to impart a reciprocating movement thereto with a predetermined number of beats per minute and means for adjusting the working pressure between the stationary plate and the movable plate, which selectively act on the stationary plate to change the mutual distance between the stationary plate and the movable plate.

[0027] In a peculiar aspect of the invention, the machine comprises electronic control means which act on the motor means to continuously change the number of beats per minute of the reciprocating motion of the movable plate both during initial start-up and during steady-state operation according to the type of product to be treated and the characteristics of the desired products.

[0028] Advantageous embodiments of the invention are obtained in accordance with the dependent claims.

Brief Description of The Drawings

[0029] Further characteristics and advantages of the invention will be more apparent upon reading of the detailed description of a preferred, non-exclusive embodiment of an improved staking machine for softening and stretching flexible sheet products, which is described as a non-limiting example with the help of the annexed drawings, in which:

FIG. 1 is a perspective view of the staking machine of the invention;

FIG. 2 is a side view of the machine of Fig. 1 ;

FIGS. 3 and 4 are broken away side views of the machine of Fig. 1 ;

FIG. 5 is a broken away top view of the machine of Fig. 1 , which shows the drive system;

FIGS. 6 and 7 are first and second block diagrams of the control of the machine of Fig. 1 .

Detailed description of a preferred exemplary embodiment

[0030] Referring to the aforementioned figures, there is shown an improved staking machine, generally designated by numeral 1 , for softening and stretching flexible sheet products, not shown, such as industrial hides and the like having opposite sides. [0031] The staking machine 1 comprises a load-bearing structure 2 which is adapted to define an entry zone 3 and an exit zone 4 for the sheet products and motorized feeding means 5 for conveying the sheet products in a predetermined longitudinal direction L from the entry zone 3 to the exit zone 4.

[0032] As is known per se, the feeding means 5 may comprise a pair of upper and lower endless conveyor belts 6, 7, tensioned by at least one pair of end rollers 8, 8', 9, 9'.

[0033] The pair of conveyor belts 6, 7 may have respective substantially straight and horizontal mutually facing portions 6', 7', for retaining the sheet products introduced into the entry zone 3 of the machine 1 and feeding them toward the exit zone 4.

[0034] The machine 1 also comprises at least one pair of mutually facing beating plates 10, 10', substantially parallel the feeding means 5 and acting on opposite sides of the products being processed.

[0035] The upper plate 10 is stationary and the lower plate 10' is movable and connected to motor means 1 1. The latter impart a reciprocating motion to the movable plate 10’ for moving it toward or away from the stationary plate 10 with a predetermined number of beats/minute.

[0036] The stationary upper plate 10 may comprise a plurality of peg tools, not shown, whereas the movable lower plate 10' may include a plurality of matingly shaped cavities or holes, also not shown, aligned with the pegs.

[0037] During the beat, the plates 10, 10' interact for the pegs and the holes to exert a pressure of predetermined value on the sheet products as they are being fed.

[0038] Obviously, the tools may also be different or have a different order, with the holes formed on the stationary plate 10 and the pegs formed on the movable plate 10', without departure from the scope of the present invention.

[0039] Advantageously, a plurality of plates 10, 10', 10" and 12, 12', 12" may be also arranged in the longitudinal direction L of the sheet products, and act on the above described belts 6, 7 at their straight portions 6', 7'.

[0040] For example, in the embodiment of the figures, that shall be intended without limitation, two sets of plates 10A, 12A may be provided, comprising a pair of stationary upper plates 10, 10”, secured to the load- bearing structure 2 and one movable lower plate 10’ and a pair of stationary upper plates 12, 12” and a a movable lower plate 12’ respectively.

[0041] As best shown in FIG. 5, the motor means 11 preferably comprise a first electric motor 13, preferably a three-phase asynchronous motor, connected to the movable plate 10', 12' via a drive mechanism 14 and a crank and connecting rod system 15, 16 or the like.

[0042] Namely, the movable lower plate 10', 12' is mounted to the upper end 17 of a connecting rod 15, which is in turn moved by a respective crank 16 the latter being coupled to the shaft 18 of the electric motor 13 via the drive mechanism 14.

[0043] As is known per se, the drive mechanism 14 may comprise one or more dive belts 19 and the crank 16 may have a circular cam.

[0044] In the illustrated embodiment, the second set of plates 12A also comprises a crank and connecting rod system 15', 16'.

[0045] The latter is coupled to the crank 16 of the first set of plates 10A via a further drive mechanism 20 composed of preferably toothed belts 21.

[0046] Thus, the second set of plates 12a is driven relative to the first set 10A and its reciprocating motion is synchronized with that of the plates 10, 10', 10" of the first set 10A.

[0047] Suitably, at least one second three-phase asynchronous electric motor 22 independent may be provided, independent of the first motor 13 and coupled to at least one of the rollers 8, 9 for moving the belts 6, 7.

[0048] The machine 1 further comprises means 23 for adjusting the working pressure between the stationary plate and the movable plate, as shown in FIG. 2. The adjustment means 23 act on the stationary plate 10, 12 and change its distance from the movable plate 10', 12'.

[0049] The adjustment means 23 may be of well-known type, for instance as described and illustrated in the European Patent EP2049694, by the proprietor hereof. [0050] In a peculiar aspect of the invention, the machine 1 comprises electronic control means 24 that act on the motor means 1 1 of the beating plates 10, 10' to continuously change the number of beats per minute of the reciprocating motion of the movable plate 10', or the movable plates 12'.

[0051] In particular, the control means 24 can change the number of beats both during initial start-up and during steady-state operation according to the type of product to be treated and the characteristics of the desired products.

[0052] The control means 24 may comprise a PLC control unit 25 operably connected to a first inverter 26 which is adapted to power the first three-phase asynchronous motor 13.

[0053] Advantageously, the control means 24 may comprise a second inverter 27 which is operably connected to the PLC control unit 25 and is adapted to control the operation of the second electric motor 22 of the feeding means 5.

[0054] Thus, the rotation speed of the second electric motor 22 and the corresponding feeding speed of the conveyor belts 6, 7 may be changed according to the characteristics of the desired product and in combination with the number of beats of the movable plates 10', 12'.

[0055] In addition, the control means 24 afford independent and continuous adjustment of the beating masses 10, 10’, 10” and 12, 12’, 12” and the feeding means 5, with no speed step changes, to effectively provide softened and stretched sheet products, without shutting down the machine 1 or alter its throughput.

[0056] A control algorithm 28 may be installed in the PLC control unit 25 and the latter may be programmed to control the first inverter 26 for the latter to operate at constant flow, during startup of the first electric motor 13, with a torque that is equal to the maximum torque.

[0057] Namely, the constant flow of the first motor 13 during startup is regulated by the first inverter 26 for frequency values of less than the nominal values of the mains frequency, equal to 50Hz.

[0058] Thus, the first electric motor 13 may operate with an acceleration ramp s having a predetermined duration and during which the first inverter 26 supplies the first motor 13 with time-modulated voltage and frequency.

[0059] With this configuration, the power consumption of the machine 1 may be reduced during startup, and motors with lower power ratings may be used.

[0060] Therefore, the first motor 13 may be appropriately sized for steady- state operation, and shall not be specially sized for startup, and smaller magnetothermic switches may be installed, as current peaks are decreased.

[0061] Furthermore, the PLC control unit 25 and the first inverter 26 may be configured to allow selection of the number of beats of the movable plate 10' or the movable plates 10', 12' in a range from 200 to 900 beats/minute, preferably from 250 to 800 beats/minute.

[0062] Advantageously, sensor means 29 may be associated with the drive mechanism 14 to detect the actual number of beats of the movable plate 10' or the movable plates 10', 12' and transmit the corresponding electric signal E to the PLC control unit 25.

[0063] The sensor means 29 are adapted to detect the rotation of the mechanism 14 and generate the corresponding electric signal E may comprise, for instance, optical or mechanical encoders or other similar sensors.

[0064] The control means 24 may comprise interface means 30 that can be accessed by an operator to set the desired number of beats and the control unit 25 may be programmed to continuously compare the desired number of beats B with the electric signal E, possibly filtered by an appropriate software filter F, using the installed algorithm 28.

[0065] Furthermore, the PLC control unit 25 will be configured to send a corresponding control signal C to the first inverter 26, which controls the operation of the first motor 13, to thereby reduce current absorption during startup.

[0066] Suitably, the staking machine 1 may comprise a switchboard 31 adapted to receive power from the mains N and operably connected to the PLC control unit 25. The latter may communicate with the interface means 30, the sensor means 29, the first 26 and second inverters 27 via cables for transmitting signals 32 using the MODBUS communication protocol or the like.

[0067] The closed-circuit control scheme that uses the sensors 29 is illustrated in the block diagram of FIG. 6, whereas the block diagram of FIG. 7 illustrates the control by the algorithm 28 of the control unit 25.

[0068] It will be appreciated from the foregoing that the improved staking machine fulfills the intended objects and particularly affords more effective and immediate adjustment of the number of beats as well as easy adaptation of the machine to the various types of product to be treated and the characteristics of the desired products.

[0069] The staking machine of the invention is susceptible of a number of changes and variants, within the inventive concept disclosed in the appended claims.

[0070] While the machine has been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

Industrial Applicability

[0071 ] The present invention may find application in industry, because it can be produced on an industrial scale in leather and hide processing factories.