PORTABLE SAWING MACHINE WITH AN ELECTRONICALLY CONTROLLED ELECTRICALLY ADJUSTABLE FOOT, FOR STRIPPING OFF BARK, ESPECIALLY CORK

PORTABLE SAWING MACHINE WITH AN ELECTRONICALLY CONTROLLED ELECTRICALLY ADJUSTABLE FOOT, FOR STRIPPING OFF BARK, ESPECIALLY CORK

The invention concerns machines for stripping bark, especially cork, from tree trunks.

It is a well-known fact that until now it has not been possible to strip bark, especially cork, from trees using a machine capable of imitating human skill.

The strength yet delicacy of a method combining muscle brain and experience has never in fact been entirely replaced by a machine, still less by one at an accessible cost.

Especially in the case of cork stripping, the main difficulty has always arisen over stopping the cutting blade the moment it reaches the underlying wood whose surface layer, called "cork cambium" is the real genera- tor of cork and, if damaged, would no longer continue to produce it.

Based on the differing conductivity between the bark and the underlying layer fed by sap, the invention here described overcomes these problems enabling a machine to be realized that, with simple and inexpensive means, strips off bark especially cork speedily and accurately, automati- caily avoiding any damage to the cambium as will now be explained.

Subject of the invention is a portable machine for stripping off bark, especially cork, that comprises a device driven by an electric motor for working a saw, another device also driven by an electric motor for working a foot that makes contact with the surface of the bark, said foot being fixed onto the end of a rod free to translate parallel to the saw, a highly conductive metal needle with handle for insertion into the trunk down to the cambium, a feeder of electric current and an electronic device with a microprocessor.

The two ends of the electric circuit generated by the feeder are connected respectively to the saw and to the metal needle. During the bark stripping operation and according to the variation in electric resistance that is created between the tip of the saw and the surface of the cambium, due to the insulating properties of the cork and to electrical conduction of the cambium fed with sap, said microprocessor operates the electric motor for the foot so as to maintain distance between its end and the tip of the saw, from one position to the next and moment by moment, substantially the same as the thickness of the cork. The purpose of this is to permit the saw to cut through the whole thickness of the cork but avoiding damage to the cambium. The electric feeder is a portable battery that generates direct current. The saw is connected to the positive pole of the electric current and the metal needle to the negative pole. The battery feeder and electronic device are housed in a container which is then stowed away inside a shoulder bag.

On said container are two sockets for cables for connecting the battery feeder and electronic device respectively to the machine and to the needle that will be pressed into the cambium in the trunk to be stripped. The direct current is passed to the saw through a stabilizing circuit and a resistance whose ends are connected to the input of a differential amplifier connected to an integrator that transforms the square wave, received due to alternate movement of the saw, into a substantially linear wave. The value of said wave is either higher or lower according to whether the saw moves in the cork or touches the cambium.

The output of said integrator is connected both to a comparator for low voltage, connected to the motor in the device operating the contact foot, and also to a comparator for high voltage connected to said motor by a pole reverser.

The foot therefore approaches the end of the saw or withdraws from it according to whether voltage is low or high so that the distance between the foot and the tip of the saw, from one position to another and moment by moment, remains equal to the thickness of the cork.

The comparators and pole reversers are connected to the motor working the contact foot by a starting and braking circuit which, on receiving current from the low voltage comparator and from the pole reverser, releases said motor and starts it in one direction or the other according to the direction of polarity.

The machine comprises an oblong body at the front that houses the devices for working the saw and the contact foot, substantially superimposed and parallel. The motor that operates the saw, in an orthogonal position, is placed in a lower oblong body within the machine.

The motor that works the contact foot, in an orthogonal position parallel to the motor operating the saw, is placed in an upper oblong body in the machine, said oblong body acting as a handle. The saw, and therefore the whole machine, is set in motion by a switch placed on the inside of the handle facing the free space between the upper and lower bodies of the machine.

In one type of execution alternate motion of the saw is obtained by a transversal mechanism having a groove within which moves the button of a crank shaft of the electric motor. Motion, in both directions, of the rod supporting the contact foot is obtained, in one type of execution, by a scroll-wormscrew mechanism connected to the electric motor by a bevel gear pair. The invention offers evident advantages. Immediate and accurate action by the foot to adjust maximum movement of the tip of the saw in relation to the outer surface of the cork, so that it corresponds to the thickness of the cork layer or in any case never exceeds it, means that an incision can be made in the bark with extreme precision down to the cambium but always avoiding any damage to it. With its rapid alternate movement the saw can quickly complete extensive and complex bark stripping as the operator need only keep the machine pressed against the bark without having to be careful not to damage the cambium. The above is therefore not only a quick and easy operation compared with present methods, but the entire layer of cork can be removed from the trunk without any risk to the cambium underneath. From the standpoints of strength and sensitivity, the stripping action here described exceeds that possible with human means given the high degree of electronic sensitivity.

The technical means incorporated make for a compact and relatively light machine.

To conclude: by using an easily operated apparatus of limited cost and bulk, bark stripping - especially in the case of cork - can be done obtain- ing a far higher rate of productivity than is possible at present.

Characteristics and purposes of the disclosure will be made still clearer by the following examples of its execution illustrated by diagrammatically drawn figures. Fig. 1 The machine complete with electronic sensor, perspective partially cut away.

Fig. 2 Diagram showing functional layout of the electronic device. Fig. 3 The machine while in use for bark stripping, perspective. Fig. 4 A diagrammatical view of the various stages of bark stripping. The machine 10 with its substantially flat square structure 11 comprises a main oblong body 12 at the front for housing a cutting device 20 with saw 35 and a regulating device 40 with fork-shaped contact foot 50 that embraces the saw for automatic adjustment of its penetration into the bark, a lower oblong body 14 and an upper oblong body 13 for respectively housing the electric motors 21 , 41 both parallel and orthogonal to the front body 12 and joined by a rear bridge 15.

The upper body 13 also acts as a handle and on the inside has a switch

16 projecting into the central free space 17 between said bodies.

The cutting device 20 comprises a motor 21 with shaft 22, fixed at whose end is a crank 23 with button 24 sliding in the crosswise groove 25 present in the bar 26 that can slide freely in the supports 30, 31 of the structure.

At the lower end of said bar is a clamp 34 to hold the saw 35 in place. The device 40 for automatic regulation of saw penetration in the trunk to be stripped, comprises a motor 41 with shaft 42 at whose end a short shaft 43 is fixed to a bevel gear 44, working as a pair with the bevel gear

45 fixed to another short shaft 46 orthogonal to the previous shaft 43.

A grubscrew 47 fixes a threaded rod 48 to said short shaft 46, said rod screwing into the scroll 49 freely sliding inside the front body 12 already described and at whose lower end is the fork-shaped foot 50 that embraces the saw 35.

Associated to said machine 10 is an electronic device 60 housed in the box 61 at whose lower end is a compartment 62 for batteries 63. On the electronic device 60 are two sockets 64, 65 respectively for connecting a cable 66 with the electric circuit of the machine 10 and a cable 87 with the strong thin needle 85, and handle 86, provided for penetrating into the cambium 91 into which sap flows.

The cable 66 is connected by a lead 67 to the motor 21 of the cutting device and another lead 68 to the output of the electronic device 60 with the motor 41 that, by means of the screw 48 and scroll 49, controls movement of the contact foot 50.

The electronic layout 70 is shown in Figure 2 and comprises electric feed from the batteries 63 through connections 71. Positive voltage stabilized by the generator 72 of stable voltage passes through resistances R_t R₂ R in series to the saw 35.

The ends of resistance R₂ are connected to the differential amplifier 73 by inputs D_f and D₂.

The output D₃ of said amplifier is connected to the integrator 74, in turn connected through output E to inputs C^nd C₂ of the comparators 75, 76 respectively for low and high voltages.

The output C₃ of the low voltage comparator 75 is connected to the circuit

77 for starting and braking the motor working the contact foot 50. The output C₄ of the comparator for high tension is connected to said circuit 77 while output C₅ is connected to circuit 77 by the pole reverser 78 through the input l₃ and the outputs and l₂.

Said reverser 78 reverses polarity of the current in accordance with the value of current in l₃.

If value l₃ is low, ^ is positive and l₂ is negative.

If value l₃ is high, is negative and l₂ is positive.

The machine operates as follows:

When the saw 35 is inserted into the cork 92, but without touching the cambium 91 through which flows sap and in which the needle 85, connected to the negative pole of the battery 63, is inserted, voltage value at the output D₃ of the differential amplifier 73 is substantially the same. If the saw 35 approaches the cambium 91 , due to diminished resistance in the cork-cambium, voltage at point D₂ is lowered and voltage at the output D₃ is proportionatly lowered as well.

As the saw 35 functions by an alternate movement, it can pass from the cork 92 to the cambium 91 and vice versa, and therefore from a less conductive means to a more conductive means, and vice versa. Consequently the voltage V at the ends of the resistance R₂ will vary in proportion alternating between a positive maximum and a value close to zero as shown in the square wave V diagram 95. The alternate voltage present on D₃ is applied to the integrator circuit 74 whose output E will produce a voltage V" approximately linear and of mean value as shown in diagram 96. This voltage V, will be of a higher value than V, as indicated in diagram 97, if the saw will be mainly cutting through the cork, and of a low value V₂ , as shown in diagram 98, if the saw penetrates too far into the cambium. If saw movement just touches the cambium but without penetrating it, voltage value E will be at an intermediate point between minimum and maximum.

During actual bark stripping if voltage at C-^ is too low, the comparator 75, through output C₃ , will start up the motor 41 through circuit 77, causing the contact foot 50 to approach the end of the saw 35. If voltage at C₂ is too high, from outputs C₄ and C₅ the comparator 76 will start rotation, through the ends h and l₂ of pole reverser 78 and the circuit 77, of the motor 41 in the opposite direction to withdraw the contact foot 50 from the end of the saw 35.

It will be seen from the foregoing that depth of saw penetration below the surface of the tree 89, will be automatically regulated to prevent any penetra-tion into the cambium 91 and its consequent deterioration. Figure 3 illustrates the machine described above during a bark-stripping operation. The figure shows the shoulder bag 55 carrying the box 61 containing the electronic device 60 and feed batteries 63. The figure also shows the saw 35 whose stroke is guided by the contact foot 50, said saw accurately following the line 90 that substantially separates the cambium 91 from the cork bark 92. The needle 86 with its tip 85 driven into the cambium 91 is also visible. Clearly, thereforee, to carry out the operation ail that is needed is to turn on electricity by pressing the switch 16 and, holding the handle 13 of the machine, guide the saw along the previously established path without risk of the incision made by the saw doing damage to the cambium 91. Figure 4 gives a diagrammatic view of how the work develops along the incision 80 made by the saw.

The figure shows the machine in the starting position A with the saw 35 about to penetrate inside the cork layer 92. In stage 80 by its alternating movement, the saw permits the machine to make its inicision B' in the surface of the trunk.

In stage C the tip of the saw 35 has made contact with the ideal line 90 that separates the cambium from the cork 92.

At this point the electronic device that determines movement of the foot towards the tip of the saw comes into effect, causing the saw to make contact with the surface 93 of the cork, keeping its maximum stroke to a point within the thickness of the layer of cork 92.

In stage D the respective positions of the foot, in relation to the tip of the saw at its maximum length of stroke, remain unaltered as, at that stage, the line 90 is substantially parallel to the surface 93 of the cork. In stage E variations in thickness of the cork layer have been exagerated to show the increased stroke made by the foot and how it approaches the tip of the saw. In stage F the positions in stage E are substantially maintained.

In stages G and H the greater thickness of the cork permits the saw to penetrate more deeply with consequentally greater the distance between the foot and the tip of the saw.

It is therefore clear that the distance between said foot and the maximum stroke of the saw will be substantially equal, from one position to the next and moment by moment, to the thickness of the cork 92. Obviously, all stages are coordinated electronically as fully described above.