Blocking device for a cutting insert on a milling machine

Abstract

 The invention concerns a blocking device for cutting inserts or knives on a milling body for working wood. The cutting body has at least one peripheral slot (12) with a deep recess (20), at an angle with respect to the flat support surface (16) of the knife (13), to be blocked with a blocking pin. This pin (14) has an upper part (22) for supporting the knife and a lower part (23), at an angle with respect to the first, extending into the bottom recess (20) at an angle that corresponds to that of said recess, said blocking pin being fastened by means of a tightening screw (15).

Description

[0001] This invention concerns milling machines with inserts for working wood, in general, and, more particularly, a blocking device for a cutting insert on a milling machine.

[0002] There already exist milling machines with cutting inserts, known also as knives and hereafter referred to by that name, which can be profiled according to necessity, place and fixed individually in slots made in the edge of the milling body, at a chosen angle.

[0003] The knives fixed to the milling body are subject to a tipping moment in the opposite direction to that in which they work, due to the resistance they encounter in cutting the wood and to a centrifugal force, deriving from the rotation of the mill. Each knife must therefore be blocked on the milling body in such a way as to resist such forces, in order to ensure the precise and steady position of the knife.

[0004] Not all the blocking systems used to date, however, have been able to resolve this problem effectively.

[0005] In one existing blocking system, the knife is fixed to the milling body with the help of a blocking pin, which is held directly against the knife, pulled or pushed by at least one tightening screw that passes through a hole in the milling body and is screwed to the pin. However, simply tightening the pin against the knife may successfully resist the tipping moment of the insert, but it is certainly less efficient against the centrifugal force.

[0006] In another blocking system, the blocking pin still presses directly against the knife, pulled by at least one tightening screw and has, on the rear, a peg or projection that interacts with an orthogonal hole in the milling body, at the base of the slot that contains the knife. In this case, the peg or projection acts as a means of resisting the centrifugal force to which the knife is subject when the milling machine is in operation.

[0007] However, this model is relatively complicated and the dimensions of the pin and, consequently, the depth of the slot in the milling body are considerable, which makes it impossible to reduce the cutting diameter of the milling machine beyond a certain point.

[0008] In another blocking system already in existence, a tightening screw is employed with a pin that has one surface divided into two separate parts; the upper plane is angled to press against the knife and the lower plane is angled against a correspondingly angled surface at the bottom of the slot for housing the knife. In this model, the blocking pin can also resist the centrifugal force to which the knife is subjected, but its use is limited to pantograph tips.

[0009] Taking into consideration all the above, the aim of the present invention is to propose a fastening device for a cutting insert or knife on a milling body, which is innovative in the shape and disposition of the blocking pin and suitable for effectively resisting both the tipping moment and the centrifugal force to which the knife is subjected, without, above all, affecting the space taken up by the pin and, consequently, the depth of the slot in which the knife and pin are mounted.

[0010] This objective is reached by a device that conforms to claim 1 and which shall be described below in more detail, with reference to the enclosed drawings, in which:

Fig. 1 shows a diagram of one part of a milling body and a separate knife and blocking pin; and

Fig. 2 shows a partial cross-section of part of the milling body with the knife held in position.

[0011] Said drawings represent part of a milling body 11, with one of its peripheral slots 12, designed to house a cutting insert or knife 13, with the help of a blocking pin 14 and at least one tightening screw 15.

[0012] Clearly, the whole milling body will have as many peripheral slots as there knives to put in them and every knife will be fixed individually in its own slot.

[0013] The slot 12 has one side (on the right in the drawings) with a flat surface 16 for pressing against the knife 13 and, at the internal end of said surface, a shoulder 17 for the support and radial positioning of said knife 13. To centre the knife 13 precisely in the slot 12, the latter has at least one reference and safety pin 18, jutting out from the flat support surface 16 and into a slotted hole 19 in the knife 13.

[0014] According to its dimensions, the knife may be equipped with a pair of parallel slotted holes for a corresponding number of reference and safety pins. Furthermore, in certain cases, especially with knives of small dimension, one single hole may accommodate two reference pins for the centering and anti-rotation of the knife.

[0015] As part of the invention, below the level of the shoulder 17, the slot 12 has a recess 20 that is angled with respect to the flat support surface 16 of the knife 13, and facing in the opposite direction (backwards) to that of the rotation of the milling machine. More specifically, said recess 20 defines an undercut 21, angled inwards below the shoulder 17, forming an obtuse angle with the support surface 16 of the knife.

[0016] The blocking pin 14 has a top part 22 with a front surface 22' for supporting and blocking the knife 13 and a lower angled portion 23 which extends into the angled recess 20 and terminates in a heel 23' that acts as fulcrum and support against the inclined undercut 21 of said recess.

[0017] The tightening screw 15 passes through a hole 24 in the milling body 11 in a perpendicular direction to the support surface 16 of the knife 13, below the shoulder 17, that is, at the level of the bottom recess 20. This tightening screw 15 turns in a threaded hole 25, situated in the lower part 23 of the blocking pin 14, in such a way as to block the latter against the knife 13 and against the inclined undercut 21.

[0018] So, the support of the portion 22 of the blocking pin 14 for the knife 13 ensures that the latter is secure against the tipping moment when the tool is in operation. On the other hand, the interaction of the heel 23' of the blocking pin 14 with the inclined undercut effectively resists the centrifugal force to which the knife 14 is subjected when the milling machine rotates.

[0019] In fact, the presence of the centrifugal force, with the blocking pin's tendency to move outwards from the milling body, is a favourable condition since it blocks the knife even more securely to the rest of the machine. At this point, the blocking pin 14 starts to act as a lever with its fulcrum at the level of its heel 23', and with the tendency of the pin to rotate with its upper part 22 towards the knife. With the tendency of the pin to move outwards, the fulcrum heel 23' begins to rise along the inclined undercut 21, causing this rotation of the blocking pin towards the knife.

[0020] The shape of the slot 12, particularly the deep recess 20 and, correspondingly, the blocking pin 14, which works as a lever because of the centrifugal force, guarantee the hold on the knife, above all, with the added advantage of minimal obstruction at the base of the pin. In fact, given the inclination of the undercut, the fulcrum of the blocking pin, represented by its heel 23', moves away from the centre of the milling machine, which means that the recess can be shallower and, without reducing the size of the knife, it is possible to build milling machines with a smaller external diameter.

Claims

1. Blocking device for cutting inserts or knives on a milling body for working wood, where the milling body (11) has a peripheral slot (12) for housing a knife (13) and a blocking pin (14) for the knife, where said slot has a flat surface (16) on one side for supporting the knife, a shoulder (17) for radial positioning of the knife and at least one safety and centering peg (18) for the knife and where said blocking pin (14) is blocked against the knife (13) by means of at least one tightening screw (15) which enters the milling body in a perpendicular direction to the flat support surface (16) of the knife and which tightens onto the pin,
characterised by the fact that:

- said peripheral slot (12) in the milling body (11) has a recess in the bottom (20), at an angle with respect to the flat support surface (16) of the knife (13),

- said blocking pin (14) has an upper portion (22) for supporting the knife and a lower portion (23) at an angle with respect to said first portion, extending into the bottom recess (20) and having a slope that corresponds to that of said recess, and

- said tightening screw (15) holds the pin at the level of said lower portion (23) and acts so as to block said upper portion of the pin against the knife and said lower portion of the pin against the side of the recess (20).

2. Device according to claim 1, in which said recess (20) defines an undercut (21), inclined inwards below the shoulder (17) for the knife, and forming an obtuse angle with the flat support surface (16) of the knife in the part where the pin presses against the knife.

3. Device according to claims 1 and 2, in which said lower portion (23) of the blocking pin (14) ends in a bottom heel (23') at a distance from the tightening screw (15), on the opposite side with respect to the upper portion, said bottom heel (23') resting against the inclined undercut to resist the centrifugal force to which the knife-blocking pin system is subject when the milling machine is in rotation.

4. Device according to claim 3, in which said bottom heel (23') acts as a fulcrum for the blocking pin, which functions as a lever, tending to rotate towards the knife when, in the presence of a centrifugal force, said heel (23') tends to rise up the inclined undercut.

5. Device according to any of the previous claims, in which the knife has at least one centering hole, orientated perpendicularly to the shoulder (17) and in which in the slot, from the support surface for the knife, there protrude one or two safety pegs, which fit into each of the centering holes.

Drawing