Device for centring, guiding and advancing a bar to be fed to a machine tool

Abstract

An apparatus (1) includes a self-centering device (2) for centering and guiding a bar (B), tube, or the like to be fed into the spindle of a machine tool. The apparatus includes a hollow housing (3) with a through-hole (5) having a longitudinal axis (X) for receiving the bar (B) to be fed into the spindle along a feeding direction (A). An inner sliding surface (4) is defined within the housing (3) and inclined relative to the longitudinal axis (X). Centering and guiding elements (6) are provided. It is housed in a hollow body (3) and shaped to contact the rod (B) and apply distributed centering and guiding action thereon; the centering and guiding element (6) is able to slide along the inner surface (4) at a distance from the longitudinal axis (X) to accommodate different rod (B) diameters; in the body (3), an elastic device (7) is housed to push the centering and guiding element (6) to a position with minimum reciprocating distance, thereby making and maintaining the centering and guiding element (6) in contact with the surface of the rod (B) during operation. A propulsion device (30) for a bar (B) is also disclosed, comprising: a support and guide member (31) configured to continuously receive the bar (B) from a first side (L1) and configured to guide the bar (B) along a propulsion direction (A); a movable gripping member (32) moving from a disengaged position (P1) and further from the member (31) to be separated from the bar (B) to a locked position (P2) closer to the support member (31) to longitudinally press the bar (B) against the support member (31) from a second opposing side (L2); and a propulsion engine device (M) configured to rotate the support and guide member (31) and / or the movable gripping member (32) at the locked position (P2) to drag the bar (B) along the propulsion direction (A).

Description

Technical Field

[0001] The present invention relates to a device for advancing, centering and guiding a bar stock to be fed into a machine tool spindle, thereby holding the bar stock in the correct axial position. Background Technology

[0002] For machining bars, tubes, or general cuboid metal parts, it is known to use feed and guide devices that function to advance the aforementioned bars into machine tools, particularly single-axis or multi-axis lathes.

[0003] The feeding device includes a propulsion device for advancing the bar stock, typically a thruster or bar propeller, configured to apply a pushing force to the rear end of the bar stock to be fed. Known types of bar propellers are described in ITMI 2009 1964.

[0004] The feeding device may also include a centering device, which functions to reduce the vibration experienced by the aforementioned bar and keep the bar in the correct axial position.

[0005] Some centering devices are known from EP0213659 and EP0485902 under the name of the applicant, while other centering devices are known from DE102014100788, GB1342133, DE29500846 and WO2017 / 149446.

[0006] Currently, machine tools (such as lathes) operate at very high rotational speeds, reaching tens of thousands of revolutions per minute or even higher. Accordingly, considering this high operating condition, it is necessary to ensure precise axial positioning and accurate feeding of the bar stock to be processed, minimizing vibrations to the bar stock to avoid equipment damage and machining errors.

[0007] Current propulsion and centering devices are not particularly effective in their propulsion and guidance functions, and cannot perform a satisfactory function of holding the bar in a fully aligned axial position.

[0008] In addition to axial propulsion, the fact that the bar also rotates around its longitudinal axis exacerbates the difficulties.

[0009] When the bars to be processed are very thin, that is, when they have very small cross sections, they are easily affected by shape instability, that is, they have a great tendency to bend during rotation due to small eccentricity and inertia, thus causing harmful impacts and stresses to the equipment in this motion.

[0010] Therefore, current bar pusher devices are almost ineffective in pushing action because the pushing action applied to the rear end of the bar is completely detrimental to controlling the bending or swaying of the bar, making it more difficult to guide and position the action of current centering devices, which often proves to be unsuitable.

[0011] The increase in the diameter of the bar does not match the reduction in the aforementioned instability and bending phenomena, because the equal increase in the rotational speed of the bar again causes the aforementioned vibration, impact, or shock problems.

[0012] Another limitation of the current device is its enormous structural and functional complexity, which is also reflected in greater financial costs and unsatisfactory mechanical reliability.

[0013] Another embodiment of the centering device is known from EP0689890 in the name of the same applicant. The device includes an idle rotating annular guide element oriented at an angle relative to the bar.

[0014] The annular guide element is pushed to adhere to the bar at points opposite each other in diameter, orients the bar by a suitable actuator, and rotates to apply a dynamic centering effect to the bar.

[0015] Similar centering devices can significantly reduce wear and noise problems caused by the impact of the bar due to the dynamic centering effect on the bar; however, such centering devices have a rather complex structure and need to be connected to a supply source suitable for the operation of the actuator of the device.

[0016] Clearly, this solution is not only structurally complex, but also inconvenient to operate, as it requires operator intervention to adjust the angle orientation of the annular guide element each time according to the diameter of the bar to be centered.

[0017] There are also centering devices, which are set with elastic blades fixed to the annular support in a cantilever manner; although such devices have a fairly simple structural configuration, they cannot satisfactorily remedy the problems of noise, bar surface damage, and, in addition, do not allow proper adjustment of the pressure exerted by the blades on the fed bar.

[0018] Based on the above, it is clear that there is significant room for improvement in the current bar centering system. Summary of the Invention

[0019] The main objective of this invention is to remedy the inherent limitations of known centering systems.

[0020] Another objective is to provide a device that is simple, effective, and reliable in both structure and function, which can significantly reduce noise and the risk of surface damage to the propulsion rod due to damping.

[0021] Specifically, the aim is to provide a self-centering device that can guide and center bars of various diameters without requiring adjustments to the device, and can also center bars of very small diameters.

[0022] Another object of the present invention is to provide a self-centering device that is easily fitted to any existing bar feed equipment, offering significant advantages in terms of cost and assembly time.

[0023] A further objective is to provide a device that is inexpensive yet high-performance, capable of advancing bars more conveniently and in the best possible way, ensuring proper positioning of the bars, and significantly reducing vibration and swaying of the bars during advancement.

[0024] The above can be achieved using the solutions defined in this invention.

[0025] The solution according to the present invention achieves all the above objectives. Attached Figure Description

[0026] These and other features of the invention will become clearer from the following description with reference to the accompanying drawings, wherein: Figure 1 It is a longitudinal cross-sectional view of a portion of the apparatus including the self-centering device for bars according to the present invention; Figure 2 and Figure 3 These are two different perspective views of the self-centering device according to the present invention; Figure 4 This is an exploded view of the self-centering device according to the present invention; Figure 5 This is a front view of the self-centering device according to the present invention; Figure 6 It is along Figure 5 A longitudinal cross-sectional view taken from plane VI-VI; Figure 7 This is a longitudinal cross-sectional view of the self-centering device in operation, showing a bar with a reduced cross-section; Figure 8 It shows that when the receiving cross-section is larger than Figure 7 The self-centering device is in operation before the bar shown in the case; Figure 9 It shows the relationship with Figure 8 The self-centering device shown is used to connect the bar to be fed. Figure 10 and Figure 11 The propulsion device included in the device according to the invention is shown in two different operating positions. Detailed Implementation

[0027] Referring to the accompanying drawings, a device 1 is shown for centering, guiding and advancing a bar (or tube or other cuboid metal element) B, which is intended to be supplied to a machine tool, particularly a lathe of the single-axis or multi-axis type.

[0028] The device 1 includes a self-centering device 2 for centering and guiding the bar stock B to be pushed onto the spindle of the lathe.

[0029] The self-centering device 2 according to the invention is configured to guide and maintain the alignment of bars or tubes on the working axis of a machine tool to accommodate bars or tubes of different diameters.

[0030] For the purposes of this specification, the term "bar" refers to any elongated linear element having a circular or polygonal, solid or tubular cross-section.

[0031] The self-centering device 2 includes a hollow housing 3 extending along the longitudinal axis X. A through hole 5 (extending along the aforementioned longitudinal axis X) is defined in the housing 3, which is adapted for the bar B to pass through so as to be fed along the feed direction A to the spindle of the lathe, or in any case to the machine tool.

[0032] In particular, the container 3 has a truncated conical shape and can be connected to the tubular element 19 of the feeding device.

[0033] If necessary, the self-centering device 2 can also be mounted on a part of the lathe. In this case, the housing 3 will be appropriately connected to the tubular part of the lathe.

[0034] In the hollow container 3, an inner sliding surface 4 is defined that is inclined relative to the aforementioned longitudinal axis X; more precisely, the inner sliding surface 4 is different in the direction of advancement of the bar B (i.e., according to the direction of advancement A).

[0035] Inside the hollow housing 3, there are multiple centering and guiding elements 6, which are shaped to interact with, i.e. contact, the rod B, and are used to apply a distributed centering and guiding effect around the rod B.

[0036] The centering and guiding elements 6 can be any desired number, for example, three or more, depending on specific needs and the functionality of the self-centering device 2. The centering and guiding elements 6 are circularly and uniformly distributed around the longitudinal axis X.

[0037] The centering and guiding element 6 can slide along the inner sliding surface 4, thereby changing its distance from the longitudinal axis X to accommodate various possible bar diameters B.

[0038] The centering and guiding element 6 can be moved from the position of minimum reciprocating distance to the position of maximum reciprocating distance to accommodate different possible diameters of the bar.

[0039] The self-centering device 2 also includes holding and guiding devices (11, 12, 13, 14) for centering and guiding element 6.

[0040] For each centering and guiding element 6, the retaining and guiding device includes a sliding groove 11 obtained along the wall of the housing 3 and a screw element 12 that engages in a hole 22 obtained on the corresponding centering and guiding element 6 and is capable of sliding along the corresponding sliding groove 11.

[0041] Each screw element 12 is formed with a rod 14 and a head 13, the rod 14 being slidable along a corresponding sliding groove 11, and the head 13 being formed as a centering and guiding element 6 for maintaining connection with the housing 3 to prevent them from separating from each other.

[0042] The self-centering device 2 includes an elastic device 7 configured to push the centering and guiding element 6 to a position with a minimum reciprocating distance, so as to maintain and keep the centering and guiding element 6 in contact with the surface of the bar B during operation. In other words, the elastic device 7 ensures that the centering and guiding element 6 is always clamped around the bar to keep the bar in the correct position.

[0043] More precisely, the elastic device includes a helical spring 7 having a base end 15 located at a position relative to the housing 3 and a movable push end 20 in contact with the centering and guiding element 6.

[0044] The helical spring 7 extends about the longitudinal axis X and has a coil with a gradually decreasing diameter in the direction from the base end 15 to the movable push end 20.

[0045] Each centering and guiding element 6 has a front end portion 8, which is adapted to intercept the front end E of the rod B. F .

[0046] An inclined promoting surface 9 is defined on the front end portion 8, which facilitates the penetration of the rod B into the receiver 3.

[0047] The inclined promoting surface 9 is shaped to receive the front end E from the rod B. F The push is designed to move the corresponding centering and guiding element 6 along the inner sliding surface 4.

[0048] The centering and guiding elements 6 each have their own rear end portions 10, and the aforementioned elastic device 7 acts on the rear end portions 10 to push the centering and guiding elements 6 against the rod B.

[0049] An annular flange 16 is also provided to hold the helical spring 7 inside the housing 3.

[0050] The annular flange 16 has a surface configured for attachment to the wider end of the housing 3 and for receiving the base end 15 of the helical spring 7 at rest.

[0051] Bearing devices 17 and 18 are also provided, which cooperate around the housing 3 and are adapted to enable the housing 3 to be rotatably connected to and housed within a portion of a tubular element 19 of a feed device or machine tool, within which the bar to be processed can be advanced.

[0052] The operation of the self-centering device 2 is now briefly disclosed.

[0053] In a static state, such as Figure 2 , Figure 3 , Figure 6 As shown, device 2 is ready to receive the bar. The centering and guiding elements 6 are positioned close to each other by the pushing action of spring 7.

[0054] Inclined surface 9 is ready to receive the front end E of bar B. F And come into contact with it.

[0055] When the rod B contacts the end 8 of the centering and guiding element 6, the rod B applies a thrust to the latter, which causes them to move and space each other in the radial direction; in other words, the centering and guiding element 6 includes a helical spring 7 and separates from each other by sliding along the inner surface 4 of the housing 3 until it reaches a position corresponding to the diameter of the rod B penetrating the housing 3.

[0056] The correct and precise movement of the centering and guiding element 6 is ensured by the threaded element 12 that cooperates with and slides along the sliding groove 11.

[0057] The inclined surface 9 facilitates the connection between the bar B and the centering and guiding element 6. Once the bar B has passed between the centering and guiding element 6, the spring 7 functions by holding the bar B on its cylindrical side surface by the adjacent surface 23 of the centering and guiding element 6.

[0058] Figure 8 and Figure 9 The operation of the self-centering device 2 is shown in the case of a larger diameter bar B'.

[0059] Due to its specific structural configuration, the centering and guiding element 6 can be independently adapted to any diameter of the bar B without any external interference.

[0060] Special Reference Figure 10 and Figure 11 The equipment 1 includes a propulsion device 30 for bar B, tube, etc.

[0061] The propulsion device 30 includes a support and guide member 31, which is configured to continuously receive the rod B on a first side L1 and to guide the rod B along the propulsion direction A.

[0062] The propulsion device 30 includes a movable gripping member 32, which can be moved by a movable member Z along a propulsion direction T that is transverse to the propulsion direction A.

[0063] The gripping member 32 can be moved from the disengaged position P1 to the locked position P2. In the disengaged position P1, it is further away from the support and guide member 31 to separate from the bar B. In the locked position P2, it is closer to the support member 31 to longitudinally press the bar B against the support member 31 from the second side L2 opposite to the first side L1.

[0064] The propulsion device 30 includes a propulsion engine device M, which is configured to rotate the support and guide member 31 and / or the movable gripping member 32 in the locked position P2 to drag and propel the bar B along the propulsion direction A.

[0065] Electric motor devices, in particular, include brushless electric motors.

[0066] The support and guide member 31 and / or gripping member 32 include a belt or strip element 33 which is wound around a pair of wheel elements 34 included in the propulsion device 30.

[0067] The wheel elements 34 are spaced apart and can rotate about a corresponding axis W arranged transversely to the propulsion direction A.

[0068] The strip or bar element 33 is shaped to contact the side surface of the bar B to apply a dragging action thereon along the pushing direction A.

[0069] During operation, when the gripping member 32 is in the disengaged position P1, a bar B of any diameter can rest on the support and guide member 31.

[0070] The moving component Z can raise the gripping component 32 to the support and guide component 31 until it reaches the locking position P2, where the bar B is gripped and held between the two components 31 and 32.

[0071] Then, the engine M can be driven to rotate the movable gripping member 32 and / or the support member 31, so as... Figure 11 The arrow indicates the propulsion rod B.

[0072] As can be clearly seen from the accompanying drawings and illustrations, the solution according to the present invention achieves all the intended objectives.

[0073] In particular, the self-centering device 2 according to the present invention is simple in structure, effective and reliable in function, and can significantly reduce noise and the risk of surface damage to the propulsion rod B due to the damping effect performed by the rectangular centering element.

[0074] The passive centering device according to the present invention is economical and versatile in operation and structure; the centering device automatically adapts to bars of various diameters, is very small, and does not require adjustment of the device itself.

[0075] In particular, the static centering effect provided by the self-centering device 2 according to the invention is more effective than the large stress borne by the bar stock B supplied to the machine tool.

[0076] Effective guidance and centering prevent impacts to bar B, eliminate any risk of surface damage to bar B, and reduce wear and noise during bar B feeding.

[0077] The self-centering device 2 according to the present invention is easily compatible with any existing bar feeding equipment, and has significant advantages in terms of assembly cost and time.

[0078] The propulsion device 30 included in the device 1 according to the invention is economical in structure but still high-performance; it can propel the bar B very conveniently and in an optimized manner, effectively ensuring its correct positioning and significantly reducing the vibration and swaying phenomena experienced by the bar during propulsion: this may be due to the bilateral gripping action and its longitudinal distribution along the cylindrical surface of the bar B, unlike conventional bar pushers, which cannot suppress swaying phenomena by acting only on the rear end of the bar.

[0079] Therefore, the propulsion device 30 included in the device 1 according to the invention is significantly more effective in propulsing, guiding and maintaining the bar B in a fully aligned axial position.

[0080] It should be understood that the description and illustrations with reference to the accompanying drawings are provided merely as an explanation of the general features of device 1; therefore, other modifications or variations may be made to the device or its components without falling outside the scope of the claims.

[0081] In particular, the geometry, dimensions and materials of one or more components constituting device 1, especially the self-centering device 2 and the propulsion device 30, can be appropriately selected and / or optimized based on specific usage requirements.

Claims

1. A self-centering device (2) for centering and guiding a bar (B) to be fed into the spindle of a machine tool, comprising: - A hollow housing (3) having a through hole (5) extending along a longitudinal axis (X) and adapted to receive and be passed through a rod (B) to be fed to the spindle in a feeding direction (A). -In the hollow container (3), an inner sliding surface (4) is defined that is inclined relative to the longitudinal axis (X). - Multiple centering and guiding elements (6), which are housed in the hollow housing (3) and shaped to contact the rod (B) and apply centering and guiding effects distributed around the rod (B). - The centering and guiding element (6) is slidably movable along the inner sliding surface (4) to change its distance from the longitudinal axis (X), thereby accommodating a variety of possible bar (B) diameters. - The centering and guiding element (6) can move from the position of minimum reciprocating distance to the position of maximum reciprocating distance to accommodate a variety of possible bar (B) diameters. - An elastic device (7) is configured to push the centering and guiding element (6) to the position of the minimum reciprocating distance so that the centering and guiding element (6) contacts the surface of the rod (B) during operation and maintains the contact between the centering and guiding element (6) and the surface of the rod (B). - The centering and guiding elements (6) are each provided with a rear end portion (10), and the elastic device (7) acts on the rear end portion (10) to push the centering and guiding elements (6) against the rod (B), and - A holding and guiding device for the centering and guiding element (6), For each centering and guiding element (6), the holding and guiding device includes a sliding groove (11) obtained along the wall of the hollow container (3) and a threaded element (12) that engages with the corresponding centering and guiding element (6) and is slidable along the sliding groove (11). Each threaded element (12) is shaped to have a rod (14) and a head (13). The rod (14) is slidable along the corresponding sliding groove (11), and the head (13) is shaped to keep the centering and guiding element (6) connected to the hollow container (3) to prevent them from separating from each other.

2. The self-centering device according to claim 1, wherein, Each of the centering and guiding elements (6) has a front end portion (8) adapted to intercept the front end (E) of the rod (B). F An inclined promoting surface (9) is defined on the front end portion (8) to facilitate the penetration of the rod (B) into the hollow housing (3), the inclined promoting surface (9) being shaped to receive the front end (E) from the rod (B). F The push is intended to move the corresponding centering and guiding element (6) along the inner sliding surface (4).

3. The self-centering device according to claim 1, wherein, The hollow container (3) has a truncated conical shape, and the inner sliding surface (4) is different depending on the direction of propulsion (A).

4. The self-centering device according to claim 1, wherein, The elastic device (7) includes a helical spring having a base end (15) in a stationary position relative to the hollow housing (3) and a movable push end (20) in contact with the centering and guiding element (6). The helical spring extends about the longitudinal axis (X) and has a coil with a diameter that gradually decreases from the base end (15) to the movable push end (20).

5. The self-centering device according to claim 4 further includes an annular flange (16) for holding the helical spring within the hollow housing (3), the annular flange (16) having a surface configured for attachment to one end of the hollow housing (3) and for continuously receiving the base end (15) of the helical spring.

6. The self-centering device according to claim 1 further includes bearing devices (17, 18) that cooperate around the hollow housing (3) and are adapted to allow the hollow housing (3) to be rotatably accommodated in a tubular element (19) of a feeding device or machine tool for advancing the bar.

7. An apparatus for feeding a bar (B) to a machine tool spindle, comprising a self-centering device (2) according to any one of claims 1-6.

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