WO2013093797A1

WO2013093797A1 - Device for locking a tool to a machine tool

Info

Publication number: WO2013093797A1
Application number: PCT/IB2012/057477
Authority: WO
Inventors: Sergio BOMBASSEI
Original assignee: B2B S.R.L.
Priority date: 2011-12-22
Filing date: 2012-12-19
Publication date: 2013-06-27
Also published as: ITVR20110231A1

Abstract

A device (1) for locking a tool to a machine tool, comprising a block (2) which can be fixed to a machine tool and forms a seat (3) for accommodating an elongated body (4) for supporting a tool (5), the block (2) forming, around the seat (3), an abutment region (5) for an annular portion (6) of the elongated supporting body (4); the block (2) comprises a first element (2a) and a second element (2b) which cooperate with each other to form the seat (3) and are mutually connected by way of traction means (7) which operate along a direction of action (100) that is substantially perpendicular to the longitudinal axis (101) of the seat (3); the seat (3) forms at least one flat abutment surface (200) for a complementary sliding wall (201) that is formed on the elongated supporting body (4), the flat abutment surface (200) being inclined with respect to the longitudinal axis (101) progressively towards the longitudinal axis (101) proceeding along the direction of insertion (102) of the elongated supporting body (4) in the seat (3); the block (2) is associated with means (10) for the movement of the elongated supporting body (4) in the insertion direction ( 102) in order to cause the locking of the elongated supporting body (4) between the first element (2a) and the second element (2b).

Description

DEVICE FOR LOCKING A TOOL TO A MACHINE TOOL

The present invention relates to a device for locking a tool to a machine tool and, in particular, to a machine tool for the removal of shavings, such as a lathe or the like, in which the piece to be worked rotates with respect to the tool.

As is known, in machine tools for the removal of shavings, the cutting edge of the tool is subject to wear and must be replaced after a preset number of minutes of work-contact or after a preset number of pieces worked.

In mass production and in other sectors, especially with tough materials such as for example steel, cast iron and similar materials, the high frequency of replacement of tools (with change times of up to 10 minutes and replacement every 30-60 minutes) results in an appreciable reduction in productivity.

In order to contain the negative incidence of the tool-changing time, solutions have been devised in order to appreciably reduce the replacement time.

For machines where the tool rotates, such as machining centers, milling machines, drills and the like, the substitution is done by employing conical male-female couplings of various dimensions (ISO 30, 40, 50, HSK and others), the angular positioning of the tool with respect to the locking device not being essential.

For machines where the piece rotates (lathes and the like), solutions aimed at reducing tool replacement times have been slower to develop, also because of the need to "maintain the fitting", i.e. to position the new tool in the same axial, radial and angular position with respect to the locking device.

Traditionally, in order to avoid dismounting of the tool (or the tool- holder) from its seat, a disassembly that requires a large amount of time and "the loss of the fitting", instead the cutting edge is substituted (or the tool bit is rotated) by operating directly on the tool in the machine: such an operation forces the technician to place his or her head inside the machine and work in a position that is uncomfortable and sometimes dangerous, with the risk of losing the tool bit, the key or the fixing screw.

About fifteen years ago locking devices appeared on the market in which the substitution of the tool or of the tool-holder occurs quickly, by operation of a single screw or cam and, in some cases, without losing the fitting corresponding to the correct positioning of the tool with respect to the locking device.

Such solutions, which are particularly innovative in conceptual terms, involve, in addition to the male-female conical coupling between the tool or the tool-holder and the locking device, an axial abutment which, for the same encumbrance, appreciably improves the rigidity of the system.

However, the solutions proposed appear extremely complex in terms of construction, as well as being delicate during their use.

In the first of these solutions in fact, the block is associated with a sleeve which forms, internally, a contoured accommodation seat, for example lobed, for an elongated body for supporting the tool or the tool- holder, the contoured seat enabling the correct angular positioning of the tool with respect to the locking device.

The outer surface of the sleeve is constituted by a male conical surface which can be mated with a female conical seat that is formed on the block which can be fixed to the machine tool.

In order to ensure the adherence between the male conical surface and the female conical seat and, at the same time, the axial abutment between a radial widening defined on the support of the tool and the abutment surface defined around the conical female seat, a cam is employed which can rotate with respect to the block and which operates on a coupling element for the actuation of a clamp which is designed to engage with the bottom of the elongated body. In this manner, the action of the technician on the cam tends to bring the elongated supporting body and the sleeve over which it is fitted into the conical female seat defined on the block.

Such operation results in the consequent elastic widening of the female conical seat in a radial direction with the consequence that, simultaneously with the axial abutment, a radial locking is achieved between the male conical surface and the female conical seat.

In fact, the elastic deformation of the female seat in a radial direction is constant only if the size of the walls of such female seat is substantially contained, preset and constant and, thus, if such female seat has a substantially cylindrical extension with a deformable stressed cross-section that is defined and adapted to the forces produced by the clamp-cam. If, as is usual in the applications described above, the block forming the female seat is prismatic, it is necessary for the intermediate deformable cylindrical sleeve that accommodates the prismatic block to have an evident reduction in rigidity and an increase in the complexity of the construction and of the parts.

The solution described, although valid from a conceptual point of view, is not however devoid of drawbacks.

First it should be noted that an extremely high level of precision is required of the size and shape of the male and female trilobate body, also with regard to the axial abutment, of the many elements constituting the locking device.

Moreover, during use of the locking device it is necessary to pay great attention in order to prevent dents which would compromise the functionality of the coupling of some components that are extremely delicate such as, for example, the male and female cones and the clamp.

Finally, it is vital to keep the device extremely clean since the presence of a foreign body, even if minute, could compromise the correct positioning and, considering the forces and the precision of the couplings, cause nicks on the parts that provide the coupling.

The use of cooling liquid further accentuates the drawback relating to the difficulty of keeping the device clean since feeding the cooling liquid, which is recycled and thus contains impurities, to the cutting edge occurs through the block on which the conical female seat with the blind end is defined, with the clamp, the cam and other kinematic interconnection elements being accommodated there.

Cleaning operations are thus extremely laborious without being able to ensure an optimal result, especially if the conical female seat (blind side) is directed downward.

The second solution, although different in terms of construction, also has drawbacks which are entirely similar.

USSN. 2008/247832 in the name of Maier Johann describes two different locking methods between tool and tool-holder.

A first embodiment, shown in Figures 1 to 3, envisages a coupling between the tool and the tool-holder block by way of interference.

The mutual orientation between tool and tool-holder is ensured by giving the male cone and the female seat an ellipse or oval shape and limiting the points of contact to four arc portions arranged in a cross. The axial force in order to push the male cone inside the female seat is provided by means of a rod with double threading (right and left) which also acts as an extractor.

It should be noted that such a system is, on the one hand, laborious and inconvenient, requiring a large amount of time in order to perform the tool change and, on the other hand, rules out the use of tools of reduced size since they would interfere with the rod.

USSN. 2008/247832 describes and illustrates in Figures 4 to 6 a second and different embodiment of the device for coupling between tool and tool-holder, which is to be used typically for tools of small dimensions.

Such a shape provides a "classic" coupling system between a shaft (tool) and a hole (tool-holder) that are oval instead of cylindrical.

The insertion of the shaft inside the hole occurs with free coupling (i.e. with play) and the radial locking occurs by way of screws or wedges.

USSN. 3704958 in the name of Gulibon Robert describes a device in which the coupling of the tool to the tool-holder occurs by way of a bracket that is defined on the tool-holder.

The device described is not a "quick-change system" but rather a system that enables, and envisages, the radial setting of the cutting edge. It appears evident that, in order to replace the tool, it is necessary to screw in and extract the screw, then rescrew and lock; such operation requires approximately at least 2-3 minutes.

The aim of the present invention is to solve the above-mentioned problems and overcome the drawbacks, by providing a device for locking a tool to a machine tool which is considerably easier and more practical to use with respect to conventional solutions.

Within this aim, an object of the invention is to provide a device for locking a tool to a machine tool which is extremely reliable in use and, especially, in which the substitution of the tool-holder is extremely quick.

Another object of the invention is to provide a device for locking a tool to a machine tool which is extremely easy to clean and in which the presence, if any, of the cooling device does not determine critical points of operation.

Another object of the invention is to provide a device for locking a tool to a machine tool which has a very low number of components so as to appreciably limit the costs of manufacture, thus making its use advantageous from an economic viewpoint as well.

This aim and these and other objects which will become more apparent hereinafter are all achieved by a device for locking a tool to a machine tool according to claim 1.

Further characteristics and advantages of the invention will become more apparent from the description of some preferred, but not exclusive, embodiments of a device for locking a tool to a machine tool according to the invention, illustrated by way of non-limiting example in the accompanying drawings wherein:

Figures 1 to 3 are side views of a sequence corresponding to the steps of locking the elongated supporting body of a tool in the locking device according to the invention;

Figure 4 is a front elevation view of the locking device coupled to the elongated supporting body;

Figure 5 is a front elevation view of the locking device;

Figure 6 is a sectional view of the locking device along the line VI-VI in Figure 5;

Figure 7 is a sectional view of the locking device along the line VII- VII in Figure 5;

Figure 8 is a side view of the elongated supporting body of the tool;

Figure 9 is a side view, rotated through 90° with respect to the previous view, of the elongated supporting body of the tool.

In the embodiments illustrated, individual characteristics shown in relation to specific examples may in reality be interchangeable with other, different characteristics, existing in other embodiments.

With reference to the figures, a device, generally designated with the reference numeral 1 , for locking a tool to a machine tool comprises a block 2 which can be fixed to a machine tool and forms a seat 3 for accommodating an elongated body 4 for supporting a tool 4b.

Conveniently, the elongated supporting body 4 is provided integral with what is called a boring bar 4a associated with one or more tools 4b.

The block 2 forms, around the seat 3, an abutment region 5 for an annular portion 6 of the elongated supporting body 4.

According to the present invention, the block 2 comprises a first element 2a and a second element 2b which cooperate with each other to form the seat 3 and are mutually connected by traction means 7 which operate along a direction of action 100 that is substantially perpendicular to the longitudinal axis 101 of the seat 3.

The seat 3 forms at least one flat abutment surface 200 for a complementary sliding wall 201 that is formed on the elongated supporting body 4.

The flat abutment surface 200 is, in particular, inclined with respect to the longitudinal axis 101 progressively towards the latter proceeding along the direction of insertion, indicated with the arrow 102, of the elongated supporting body 4 into the seat 3.

The block 2 is associated with means 10 for the movement of the elongated supporting body 4 in the insertion direction 102, in order to cause the locking of the elongated supporting body 4 between the first element 2a and the second element 2b.

Advantageously, the movement of the elongated supporting body 4 in the insertion direction 102 owing to the movement means 10 is contrasted elastically by the action applied between the first element 2a and the second element 2b by the traction means 7.

With reference to the embodiment shown in the figures, the block 2 can be fixed, to the machine tool, and typically to the slider or to the turret, with removable means 14 for fixing, which will be better described hereinbelow, and which conveniently protrude from a coupling surface formed on the first element 2a.

In order to render the coupling of the elongated supporting body 4 in the seat 3 extremely practical and effective, the seat 3 is delimited, at the first element 2a, by a first abutment plane 8a for a first coupling wall 18a formed on the elongated supporting body 4 and, conveniently, by a second abutment plane 8b for a second coupling wall 18b.

Specifically, the first abutment plane 8a and the second abutment plane 8b are arranged so as to be angularly mutually spaced and substantially parallel to the longitudinal axis 101.

Advantageously, the seat 3 is delimited, at the second element 2b and on opposite sides with respect to the flat abutment surface 200, by respective delimiting surfaces 9 a and 9b, which are not intended to come into contact, during the steps of insertion or withdrawal, with portions of the elongated supporting body 9.

The movement means 10 are adapted to move, on command, the elongated supporting body 4 also in an opposite direction with respect to the insertion direction 102 in order to cause the release of the elongated supporting body 4 from the locking device 1 and, in particular, from the block 2.

According to a preferred embodiment, the movement means 10 comprise a cam 11 which is connected to an actuation head 12 which can move, as a consequence of rotation of the cam 11 about its own actuation axis 103, along a direction that is substantially parallel to the longitudinal axis 101 in order to operate by pushing against a first shoulder 13a, in the locking step, or against a second shoulder 13b, in the release step, the first shoulder 13a and the second shoulder 13b being formed on the supporting body 4.

In particular, between the first shoulder 13a and the second shoulder 13b there is a transverse recess 13 formed along the complementary sliding wall 201.

The actuation head 12, during the locking step, is brought, thanks for example to the action of a pin 15 which is carried by the second element 2b and is slideable along a groove 16 formed on the outer surface of the cam 11 , closer to the longitudinal axis 101 so as to distribute the thrust action over a surface which is larger than the first shoulder 13a.

As previously mentioned, the locking device 1 has removable means 14 for fixing the block 2 to the machine tool.

Such removable means for fixing 14 can be constituted by at least first and second centering pins 17 which are accommodated in the first element 2a and have a first end 17a that protrudes from the first element 2a in order to be inserted in a respective centering seat formed on the machine tool and a second end 17b, which can be conveniently inserted with interference into a respective insertion seat that is formed on the second element 2b.

Moreover, the removable means 14 for fixing comprise at least one first fixing screw 14a and one second fixing screw 14b, which are arranged on opposite sides with respect to the seat 3.

In order to make the forces more balanced it is advisable to provide, as shown in the figures, at least two first fixing screws 14a and at least two second fixing screws 14b.

The first and second fixing screws 14a and 14b are guided through a respective guide 15 which is formed in the second element 2b and in the first element 2a and are engageable, with a respective threaded end portion 14c, in a female thread portion formed on the machine tool.

The first and the second fixing screws 14a and 14b advantageously provide, in addition to the means for removable fixing 14, the traction means 7 as well.

The traction means 7 can, in turn, be constituted or completed by at least one first traction screw 7a and one second traction screw 7b which have an actuation head 7c which operates on an abutment that is formed on the second element 2b and a threaded shank 7d which is coupled in a respective coupling seat provided on a respective pin 17.

The operation of the locking device 1 is as follows.

After insertion of the first end 17a of the centering pins 17 in the respective centering seat formed on the machine tool, an operation which is carried out when mounting it, the elongated supporting body 4a is inserted in the seat 3 with the cam 11 in the angular position shown in Figure 1 : inside the block 2 the actuation head 12 of the cam 11 , protruding from the flat abutment surface 200, determines the initial axial position of the tool- holder boring bar or of the tool.

In this condition the annular portion 6 of the elongated supporting body 4 is uncoupled from the abutment region 5 by approximately 1 mm.

The cam 11 rotates through a first angle (for example 90° in a clockwise direction about the actuation axis 103) in order to arrive at the angular position shown in Figure 2: thanks to the action of the actuation head 12 which is associated with the cam 11 on the first shoulder 13 a, the annular portion 6 of the elongated supporting body 4 approaches the abutment region 5 thus arriving, indicatively, at a distance of approximately 0.5 mm.

The cam 11 , as a result of the rotation, comes closer to the longitudinal axis 101 guided by the pin 15, thus achieving a correct coupling between the actuation head 12 and the first shoulder 13 a.

The cam 11 further rotates through 60° - 80° in the clockwise direction with a preset torque so as to arrive at the position shown in Figure 3.

The operation of the actuation head 12 pushes the elongated supporting body 4 along the direction of insertion 102, elastically loading the traction screws 7a and 7b and the fixing screws 14a and 14b which were preventively preloaded and provide the traction means 7.

The penetration of the elongated supporting body 4 continues until the annular portion 6 of the elongated supporting body 4 is brought into abutment against the abutment region 5 formed on the block 2.

In this condition the boring bar constitutes a single body with the block and the cross-section that reacts to the forces exerted on the cutting edge becomes that of the annular portion of the boring bar.

The disassembly of the tool-holder boring bar or of the tool occurs in the following manner:

the cam 11 rotates through 150° - 170° in the anticlockwise direction so that the actuation head 12 operates by pushing on the shoulder 13b so as to release the elongated supporting body 4 from the respective seat 3; the tool-holder boring bar 4a or the tool 4b is extracted, and the mating surfaces are cleaned with compressed air or clean cooling liquid.

It has been found that the locking device 1 according to the invention allows the following:

- substitution of the tool-holder boring bar or of the tool in a short time,

- positioning of the new cutting edge at the same point (in the working surface) as the worn one "without losing the fitting",

- thanks to the conical coupling supplemented by the axial abutment, transfer of the stressed cross-section of the boring bar from the diameter of the prism to the diameter of the abutment,

- excellent cleaning of the surfaces for coupling without excessive difficulty thanks to the fact that the female seat is completely free on the bottom.

Another advantage of the locking device according to the invention lies in the simplicity of construction, since it is made up (excluding the screws) of just five simple components as opposed to the over 10-15 devices commercially available nowadays.

Specifically, it has been found that the locking device 1 according to the invention is, to all effects, a quick-change system and:

- it enables substitution of the tool in a short time (10-15 seconds);

- the new cutting edge is positioned at the same point of the working surface as the worn one;

- the coupling between the tool and the tool-holder block is achieved by maximizing rigidity through the elastic radial deformation of a portion of the block and the axial deformation of the screws thus moving, in the axial direction, the annular portion of the elongated body into abutment against the abutment region. The speed of substitution is ensured thanks to the use of cam-based means of locking and movement, the repeatability of the position of the new cutting edge deriving from the non-circular shape of the elongated supporting body and of the respective seat formed on the block, while the rigidity from the conical connection is ensured by interference.

In summary, in the device according to the invention the block is provided by a first element and by a second element which are mutually connected by way of traction means.

The operation of deformation, which is necessary to ensure the rigidity by interference during the step of inserting the elongated body into the seat, is discharged onto the traction means which are elongated during the step of insertion.

All the characteristics of the invention, indicated above as advantageous, convenient or similar, may also be missing or be substituted by equivalent characteristics.

The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

Thus, for example, it is possible to associate the locking device 1 with a device for feeding the cooling liquid 20 which can have an elongated body that leads, at the bottom of the seat 3, into a feeder opening arranged in a position corresponding to an outlet of a feeder conduit formed along the boring bar holder 4a.

In practice it has been found that in all the embodiments the invention has achieved the intended aim and objects.

In practice the materials employed may be any, according to requirements.

Moreover, all the details may be substituted by other, technically equivalent elements.

The disclosures in Italian Patent Application no. VR2011A000231 from which this application claims priority are incorporated herein by reference.

Where the technical features mentioned in any claim are followed by reference numerals and/or signs, those reference numerals and/or signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference numerals and/or signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference numerals and/or signs.

Claims

1. A device (1) for locking a tool to a machine tool, comprising a block (2) which can be fixed to a machine tool and forms a seat (3) for accommodating an elongated body (4) for supporting a tool (5), said block

(2) forming, around said seat (3), an abutment region (5) for an annular portion (6) of said elongated supporting body (4), characterized in that said block (2) comprises a first element (2a) and a second element (2b) which cooperate with each other to form said seat (3) and are mutually connected by way of traction means (7) which operate along a direction of action (100) that is substantially perpendicular to the longitudinal axis (101) of said seat

(3) , said seat (3) forming at least one flat abutment surface (200) for a complementary sliding wall (201) that is formed on said elongated supporting body (4), said flat abutment surface (200) being inclined with respect to said longitudinal axis (101) progressively towards said longitudinal axis (101) proceeding along the direction of insertion (102) of said elongated supporting body (4) in said seat (3), said block (2) being associated with means ( 10) for the movement of said elongated supporting body (4) in the insertion direction (102) so as to cause the locking of said elongated supporting body (4) between said first element (2a) and said second element (2b).

2. The locking device (1 ) according to claim 1, characterized in that the movement of said elongated supporting body (4) in the insertion direction (102) owing to said movement means (10) is contrasted elastically by the action applied between said first element (2a) and said second element (2b) by said traction means (7).

3. The locking device (1) according to one or more of the preceding claims, characterized in that said block (2) comprises a means (14) for removable fixing to said machine tool.

4. The locking device according to one or more of the preceding claims, characterized in that said seat (3) is delimited, at said first element (2a), by a first abutment plane (8a) for a first coupling wall (18a) that is formed on said elongated supporting body (4).

5. The locking device according to one or more of the preceding claims, characterized in that said seat (3) is delimited, at said first element i (2a), by a second abutment plane (8b) for a second coupling wall (18b), said first abutment plane (8a) and said second abutment plane (8b) being arranged so as to be angularly mutually spaced and substantially parallel to said longitudinal axis (101).

6. The locking device according to one or more of the preceding I claims, characterized in that said movement means (10) are adapted to move, on command, said elongated supporting body (4) also in an opposite direction with respect to said insertion direction (102) in order to cause the release of said elongated supporting body (4) from said locking device (1).

7. The locking device according to one or more of the preceding i claims, characterized in that said movement means (10) comprise a cam (11) which is connected to an actuation head (12) which can move, as a consequence of the rotation of said cam (11) about its own actuation axis (103), along a direction that is substantially parallel to said longitudinal axis (101) in order to operate by pushing against a first shoulder (13a) or against I a second shoulder (13b) between which there is a transverse recess (13) formed along said flat abutment surface (200).

8. The locking device according to one or more of the preceding claims, characterized in that said cam (11) can move, as a consequence of rotation about its own actuation axis (103), along a direction that is

• substantially perpendicular to said longitudinal axis (101).

9. The locking device (1) according to one or more of the preceding claims, characterized in that said removable means (14) for fixing said block (2) to said machine tool comprises at least one first fixing screw (14a) and one second fixing screw (14b), which are arranged on opposite sides with

' respect to said seat (3) and are guided through a respective guide (15) which is formed at least in said second element (2b), said first and second fixing screws (14a, 14b) being able to engage, with a respective threaded end portion (14c), in a female thread portion formed in said machine tool.

10. The locking device (1) according to one or more of the preceding claims, characterized in that said removable means (14) for fixing said block (2) to said machine tool comprise first and second centering pins (17) which are accommodated in said first element (2a) and have a first end (17a) that protrudes from said first element (2a) in order to be inserted in a respective centering seat that is provided on said machine tool.

11. The locking device (1) according to one or more of the preceding claims, characterized in that said centering pins (17) have a second end (17b) which can be inserted with interference within a respective insertion seat formed on said second element (2b).

12. The locking device (1) according to one or more of the preceding claims, characterized in that said traction means (7) comprise at least one first traction screw (7a) and one second traction screw (7b) which have an actuation head (7c) which operates on an abutment that is formed on said second element (2b) and a threaded shank (7d) which is coupled in a pin (17) which is accommodated in a receptacle formed in said first element (2a).

13. The locking device (1) according to one or more of the preceding claims, characterized in that said traction means (7) comprise said at least one first and second fixing screws (14a, 14b).