Centering device for supplying a bar to a machine tool

Abstract

A centering device (1;101;201;1A, 1B, 1C, 1D) for centering a bar (2), tube or similar supplied to a machine tool spindle comprises: a support base (3;3A, 3B, 3C, 3D) having a through-opening (4) for the passage of the bar (2); oval centering elements (5;105;205;5A, 5B, 5C, 5D) rotatably connected to the support base (3;3A, 3B, 3C, 3D) and circumferentially arranged to maintain the bar (2) axially aligned on the machine tool spindle; and elastic means (7) arranged to elastically bias the oval centering elements (5;105;205;5A, 5B, 5C, 5D) to radially gathered and retracted positions close to each other.

Description

Technical Field

[0001] The present invention relates to a centering device for guiding a bar, tube or the like supplied to a machine tool and maintaining it in a correct position in the axial direction.

Background Art

[0002] Especially in the field of machine tools such as single-spindle or multi-spindle lathes, the use of various centering devices is known whose function is to reduce oscillation and correct the positioning of semi-finished metal products of elongated shape such as bars, tubes and the like.

[0003] Some examples of such devices are known from Patent Document 1 and Patent Document 2 of the applicant of the present application.

[0004] In recent years, machine tools, especially lathes for processing bars and the like, operate at very high rotational speeds that can reach values of 10,000 rpm or more. In view of this feature, it has not been proven that current centering devices are particularly effective in their operation of guiding and maintaining a bar rotating about its longitudinal axis in an axially aligned position during supply.

[0005] In other words, the centering operation provided by the aforementioned known devices appears to be very gentle and insufficient to counteract the large stresses to which the bar is subjected due to small irregularities or deflections of the bar.

[0006] Inappropriate guiding and centering operations are the cause of bar knocking, causing high levels of wear and noise in the supply system and often resulting in surface damage to the bar.

[0007] Another centering device known from Patent Document 3 of the applicant of the present application comprises a rotating annular guide element that idles and can be angularly oriented with respect to the bar.

[0008] The annular guide element is brought into close contact with and pressed against the bar at diametrically opposite points by orienting the annular guide element with a suitable actuator, and is rotationally dragged to exert a dynamic centering action on the bar.

[0009] Similar centering devices can significantly reduce problems of wear and noise caused by knocking of the bar for the dynamic centering operation on the bar, but the structure is rather complex and requires a connection to a suitable power source to enable operation of the actuator of the device.

[0010] Also, it is necessary to adjust the angular orientation of the annular guide element each time according to the diameter of the bar to be centered, which thus involves the intervention of an operator.

[0011] There are also centering devices having a fixed elastic plate cantilever-supported on an annular support. These devices have a sufficiently simple structural configuration, but cannot satisfactorily overcome problems of noise and surface damage to the bar, and furthermore do not allow appropriate adjustment of the pressure exerted on the bar by the plate.

[0012] In view of the above, there is sufficient room for improvement in the bar centering system.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0014] The main object of the present invention is to overcome the limitations inherent in known centering systems.

[0015] Another object is to provide, at the same time, a centering device that is structurally simple, functionally effective, reliable, and significantly reduces the risk of braking action, noise, and surface damage to the advancing bar.

[0016] Yet another object is to provide an operationally and structurally inexpensive technical solution, which is also highly versatile, i.e., it can guide and center bars of different diameters without the need to adjust the device, and can also center bars of very small diameters.

[0017] A further object of the present invention is to provide a centering device that easily adapts to any existing bar supply device, having clear advantages in terms of cost and assembly time. This is achieved by the centering device according to claim 1.

Means for Solving the Problems

[0018] The above can be achieved by the centering device according to claim 1.

[0019] All of the above objects are achieved by the centering device according to the present invention.

[0020] These and further features of the present invention will become more apparent from the specification with reference to the accompanying drawings shown below.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0022] Referring to the accompanying drawings, a centering device (1; 101; 201; lA, 1B, lC, lD) for centering a centering bar 2, a tube or the like supplied to a spindle of a machine tool such as a lathe is shown. The centering device according to the present invention is configured to guide and maintain a bar or tube aligned on the machining axis of a machine tool and is also compatible with bars or tubes of different diameters.

[0023] For the purposes of this specification, the term "bar" means any elongated linear element having a circular or polygonal, solid or tubular cross-section.

[0024] Hereinafter, with reference to FIGS. 1 and 2, a first embodiment of the centering device 1 will be disclosed.

[0025] For other embodiments, as shown in FIGS. 2 to 10, the description will be limited only to the differences from the first embodiment.

[0026] For similar parts or components common to the various embodiments, the same reference numbers are used, or the numbers are incremented by 100 or 200 only, or by adding letters to the numbers.

[0027] Referring to the first embodiment defined in FIGS. 1 and 2, the centering device 1 comprises a support base 3 along which a through opening 4 for the passage of the bar 2 is obtained, which is aligned on each spindle of the machine tool.

[0028] The support base 3 can in particular be formed as a tubular guide member for the bar 2, which is part of a supply device not shown, or from a hub fixed to a plate or a cradle, or as a support fixed to the guide carriage of a different bar supply device, or as any other suitable support element.

[0029] The centering device 1 comprises a plurality of conical centering elements 5 which are rotatably connected to the support base 3 and are arranged circumferentially thereon to form a cone as a whole.

[0030] Each conical centering element 5 comprises, at a first end El, a connecting part 8 which is hinged to a corresponding connecting part 9 obtained on the support base 3.

[0031] In particular, the connecting part 9 is obtained by a protruding zone which engages in a complementary manner with a recessed zone obtained on the connecting part 8 of each conical centering element 5.

[0032] A hinge pin 15 is provided which connects the connecting part 8 and the connecting part 9 and at the same time enables the corresponding rotation.

[0033] Thus, each conical centering element 5 can rotate about its respective hinge pin 15, as indicated by the arrow R.

[0034] In particular, the conical centering element 5 is defined by the finger elements 5. The finger elements 5 have a tapered shape and, in particular, have a decreasing cross-section starting from a first end E1 close to the support base 3.

[0035] The conical centering element 5, or the finger conical centering element, contacts the surface of the bar 2 and is arranged so as to exert a guiding action in a direction axially aligned with the spindle on the lathe of the machine tool.

[0036] The centering device 1 comprises elastic means 7 arranged to elastically bias the finger elements 5 towards the reverse assembly position. In other words, thanks to the elastic means 7, the finger elements 5 tend to arrange themselves in a radially contracted configuration in which they approach each other. The elastic means 7 then act to bias the finger elements 5 towards the longitudinal axis Y of the support base 3. In particular, in the contracted position with respect to each other, the finger elements 5 incline and converge towards the longitudinal axis Y.

[0037] In one embodiment, the elastic means comprise a toroidal elastic element 7 wound around the finger centering element 5.

[0038] The toroidal elastic element 7 can be an elastic strip or an annular coil spring or another equivalent shape.

[0039] In the first embodiment of FIGS. 1 and 2, the spring 7 is held in a position coupled to the finger element 5 by the retaining projection means 14.

[0040] The projection means particularly comprise a screw element 14 screwed into the finger element 5, the head of which functions as a stationary and retaining element for the toroidal elastic element 7.

[0041] According to another embodiment (the embodiment of FIGS. 3 and 5), the elastic element 7 is received inside an annular groove 13 obtained on the outer surface of the finger element 5.

[0042] With the above configuration, in particular, by means of the elastic means 7 clearly made for the conical centering element 5, the strength of the pressure exerted by the element 5 on the bar 2 can be adjusted. To adapt to the specific configuration of the bar to be supplied, it is sufficient to replace the elastic element 7 with another having the desired mechanical characteristics.

[0043] Each conical centering element 5 is provided, at its second end E2, which is free and opposite to the first end E1, with a contact portion 10 suitable for contacting the bar 2 and exerting a guiding and centering action on the bar 2.

[0044] The finger centering element 5 can be provided with friction reducing means F configured to reduce friction and facilitate the corresponding sliding of the bar 2 thereon. M

[0045] In one embodiment, the friction reducing means F M comprises an insertion portion 11 (shown in Figure 3) obtained on the contact portion 10. The insertion portion 11 consists of, for example, an anti - adhesion material having a low coefficient of friction (such as polytetrafluoroethylene, or another suitable anti - friction material), is intended to contact the bar 2, and facilitates its sliding with respect to the corresponding finger element 5.

[0046] In another embodiment shown in Figures 5 and 6, the friction reducing means F M includes rotation means 12.

[0047] In particular, the rotation means comprises, for each finger element 5, a rotary bearing 12, the axis of rotation X of which is inclined with respect to the axial plane Px of the support base 3.

[0048] The rotary bearings 12 are rotatably supported on respective shank projections 30 projected by the respective conical centering elements 5.

[0049] ​These shank projections 30 are each connected to the respective conical centering element 5 in an adjustable manner by suitable fixing means, and by loosening the latter, it is possible to change the orientation of each axis X. In this way, the position and inclination of the rotary bearing 12 can be selected in a desired manner according to specific functional needs and based on the geometry of the semi-finished product (e.g., bar) guided when supplying the machine tool.

[0050] Due to this specific inclined arrangement, the rotary bearing 12 can exert an effective centering and guiding action, and at the same time, the friction caused by the corresponding movement of the bar 2 relative to the contact portion 201 of the finger element 5 can be significantly reduced.

[0051] The numbers of the finger elements or conical centering elements can be selected according to specific needs.

[0052] For example, as shown in FIG. 7, two finger elements 5A can be provided for the centering device 1A according to the present invention.

[0053] In FIG. 8, an embodiment of the centering device 1B having three finger elements 5B is schematically shown.

[0054] In FIG. 9, an embodiment of the centering device 1C having four finger elements 5C is schematically shown.

[0055] In FIG. 10, an embodiment of the centering device 1D having six finger elements 5D is schematically shown.

[0056] Depending on the shape of the cross-section of the bar 2, embodiments are possible using more finger centering elements.

[0057] All of the above-described embodiments have a similar structural composition of the support base 3, particularly the part for coupling to the feeder, with reference to FIGS. 1 to 10.

[0058] The support base 3 is configured to support and guide the rotating bar by instantaneously adapting to the angular velocity fluctuations of the spindle of the machine tool.

[0059] Precisely, the support base 3 is rotatably supported by a cylindrical element 16, while the cylindrical element 16 is supported by a feeding device in a non-rotatable manner about its axis.

[0060] In this way, the rotational inertia of the centering device 1 is significantly reduced with respect to the conventionally known solutions and has all the above-mentioned distinct advantages regarding the accuracy of the machining operations performed on the bar 2.

[0061] The relative rotation between the support base 3 and the cylindrical element 11 is achieved by interposing appropriate rolling means therebetween.

[0062] More precisely, an annular shoulder 17 is provided at the rear end portion of the support base 3, facing in the opposite direction to the spindle of the machine tool, and a first ball bearing 18 inserted into the support base 3 from the front end portion facing the annular shoulder 17 is disposed.

[0063] A second ball bearing 19 is provided on the support base 3 and is inserted at an appropriate distance from the first bearing 18 by a spacer 20 so as to ensure the stability with respect to the centering device 1.

[0064] In front of the second ball bearing 19, the support base 3 is provided with an annular recess 21 into which an elastic ring 22 of the snap ring type is inserted to hold the positions of the two bearings 18, 19 and the spacer 20.

[0065] The support base 3 is detachably fixed to the cylindrical element 16 of the centering device 1.

[0066] In particular, at the front end of the cylindrical element 16, there is provided an annular inner coupling seat 23 into which the bearings 18, 19 provided on the support base 3 are inserted when the support base 3 is fitted to the cylindrical element 16 of the devices 1, 101, 201.

[0067] The support base 3 is removably fixed to the cylindrical element 16, for example, by an outer sleeve 24 having an inner annular edge 24 at the front end, which is intended to contact the second bearing 19 arranged on the front surface of the support base 3.

[0068] Once the outer sleeve 24 of the support base 3 is fitted to the cylindrical element 16, the outer sleeve 24 is inserted into the cylindrical element 16 and acts on the bearing 19 placed on the front surface by its inner edge 24' to provide an anti - detachment effect on the support base 3, and is arranged outside the support base 3.

[0069] The outer sleeve 24 is fixed to the cylindrical element 16, for example, by a series of grub screws 25 inserted into appropriate screw holes provided in the sleeve 24, or by other suitable fixing means, enabling the easy removal of the centering device 1.

[0070] During operation, the finger elements 5 pushed forward by the bar 2 rotate by an appropriate amount around their respective hinge zones and adapt to the part of the bar 2, in contrast to the return elastic action of the elastic means 5. Then, the bar 2 moves forward without being damaged by the rear bar extrusion element, and at the same time, the stress generated during rotation is relieved. When the entire length of the bar passes through the centering device 1, the finger elements 5 are further opened under the thrust of the rear bar extrusion element, which generally has a larger cross - section than the bar 2, enabling a partial forward movement of the bar towards the lathe.

[0071] From what has been described so far and what is shown in the accompanying drawings, it is clear that the centering device according to the present invention achieves all the established objectives.

[0072] In particular, the centering device according to the present invention is structurally simple, functionally effective and reliable, and at the same time, it is noted that the damping action, noise and risk of surface damage to the advancing bar executed by the conical centering element are significantly reduced.

[0073] The passive centering device according to the present invention is operationally and structurally inexpensive, and is also very versatile and can effectively adapt to various bars with very small diameters without the need for adjustment of the device.

[0074] The centering device according to the present invention can be easily adapted to any existing bar feeding device and is clearly advantageous in terms of cost and assembly time.

[0075] What has been described so far and what has been shown with reference to the accompanying drawings are provided merely as examples of the general features of the centering device, and thus it is understood that other modifications or variations can be made to the device or its parts without departing from the scope of the claims.

[0076] In particular, the geometric structure, dimensions, position, and material constituting one or more parts of the device 1 can be optimized and / or selected based on specific usage requirements.

Claims

1. A centering device (1; 101; 201; 1A, 1B, 1C, 1D) for centering a bar (2) supplied to a spindle of a machine tool, a support base (3; 3A, 3B, 3C, 3D) provided along a through-opening (4) for passing the bar (2), conical centering elements (5; 105; 205; 5A, 5B, 5C, 5D), and these conical centering elements are rotatably connected to the support base (3; 3A, 3B, 3C, 3D) and arranged around the support base to maintain the bar (2) at the center of the spindle, elastic means (7) are provided to elastically bias the conical centering elements (5; 105; 205; 5A, 5B, 5C, 5D) towards each other to a radially converging position, Each of said conical centering elements (5; 105; 205; 5A, 5B, 5C, 5D) is provided with friction reducing means (F Ｍ ) which comprises rotating means configured to facilitate the corresponding sliding of said bar (2) relative to said conical centering element. the rotating means comprises at least one rotary bearing (12) having a rotation axis (X) inclined with respect to the longitudinal axis (Y) of the support base (3; 3A, 3B, 3C, 3D), and each rotary bearing (12) is rotatably supported by a respective shank protrusion (30) protruding from a respective one of the conical centering elements (5; 105; 205; 5A, 5B, 5C, 5D), the shank protrusion (30) is connected to a respective one of the conical centering elements (5; 105; 205; 5A, 5B, 5C, 5D) in an adjustable manner by suitable fixing means, so that the direction of the rotation axis (X) is changed and the position and inclination of the rotary bearing (12) are selected based on the geometric shape of the bar (2) for guiding the bar (2) to the machine tool. A centering device as described above.

2. The centering device according to claim 1, wherein each of the conical centering elements (5; 105; 205; 5A, 5B, 5C, 5D) comprises a connecting portion (8) hinged to a corresponding coupling portion (9) provided on the support base (3; 3A, 3B, 3C, 3D) at a first end (E1).

3. The centering device according to claim 1 or 2, wherein the elastic means (7) comprises a toroidal elastic element wound around the conical centering elements (5; 105; 205; 5A, 5B, 5C, 5D) and configured to bias the conical centering elements towards each other with respect to the longitudinal axis (Y) of the support base (3, 3A, 3B, 3C, 3D).

4. The centering device according to claim 3, wherein an annular groove (13) is provided in the conical centering element (5; 105; 205; 5A, 5B, 5C, 5D), and the toroidal elastic element is accommodated inside the annular groove (13).

5. The centering device according to claim 3, wherein the conical centering element (5; 105; 205; 5A, 5B, 5C, 5D) is provided with holding projection means (14) for holding the toroidal elastic element at a position joined to the conical centering element (5; 105; 205; 5A, 5B, 5C, 5D).

6. The centering device according to claim 5, wherein the holding projection means (14) comprises screw elements screwed into the conical centering element (5; 105; 205; 5A, 5B, 5C, 5D), and the head of each of the screw elements acts as a support and holding element for the toroidal elastic element.

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