Storage unit for holding bar material

Abstract

Bearing unit (10) for receiving bar stock, comprising a shaft (12) and a sleeve (14), wherein the shaft (12) is mounted within the sleeve (14) by means of at least one radial bearing (20, 22) and is supported on an axial bearing (24), wherein the at least one radial bearing (20, 22) has an inner ring and an outer ring, wherein the shaft (12) is arranged axially displaceably within the sleeve (14) and wherein, furthermore, at least one spring element (34) for absorbing axial forces is arranged between the axial bearing (24) and the shaft (12) and / or between the axial bearing (24) and the sleeve (14), characterized in that the shaft (12) has a first step (S1), by means of which the shaft (12) is supported on the inner ring of the first radial bearing (20) and / or that the shaft (12) has a second step (S2), which serves as Contact surface by means of which the shaft (12) is supported on the axial bearing (24).

Description

[0001] The invention relates to a bearing unit for holding bar stock, in particular by means of a clamping sleeve. Such bearing units, also referred to as clamping sleeve bearings, are arranged in loading magazines of machine tools and serve as a connecting element between a clamping sleeve and a feed rod for feeding the bar stock to the machine tool for the purpose of machining. The machine tool can in particular be a lathe, such as a multi-spindle lathe, a long-turn lathe, or a short-turn lathe. The bar stock is often cylindrical, but can also have polygonal or other arbitrarily shaped cross-sections in addition to round ones.

[0002] Corresponding clamping sleeves for use in a bar feed are shown, for example, in the Schlenker product catalog in the 2014 edition on pages 30 to 31.

[0003] Previous bearing units according to the state of the art have a shaft that serves to secure a clamping sleeve for holding bar stock. The bar stock is rotatably mounted and usually rotates at speeds between eight thousand and ten thousand revolutions per minute. For this purpose, the shaft is mounted within a sleeve by means of two radial ball bearings. To absorb axial forces that occur during machining and while holding the bar stock, an additional axial bearing is provided within the sleeve of the bearing unit, on which the shaft is axially supported. Such bearing units are disclosed in the publications DE 36 34 364 A1, DE 11 24 322 A, and in the Japanese utility model documents JP S51 - 69 981 U and JP S53 - 1 670 Y2.

[0004] A disadvantage of previous bearing units, however, is that due to axial forces, which primarily occur during the loading or threading of new bar stock, the thrust bearing fails within a relatively short period of time, requiring the entire bearing unit to be replaced. Since the failure of the thrust bearing often goes unnoticed and the balls, which serve as rolling elements of the thrust bearing, wear out, the result is friction welding of the shaft and sleeve, and the conveyed bar stock can no longer be rotated. This often leads to consequential damage to the machine tool or the loading magazine.

[0005] It is therefore the object of the invention to provide a bearing unit for receiving bar stock which is capable of absorbing high axial forces which may occur when receiving new bar stock and thus ensuring a longer service life of the bearing unit.

[0006] This object is achieved according to the invention by a bearing unit having the features of claim 1. Preferred embodiments and further advantageous features of the invention are specified in the dependent claims.

[0007] A bearing unit for receiving bar stock is described, which has a shaft and a sleeve, wherein the bar stock is fastened to the shaft, for example by means of a clamping sleeve, wherein the shaft is mounted within the sleeve by means of at least one radial bearing and is supported on an axial bearing. According to the invention, the shaft is arranged so as to be axially displaceable within the sleeve, and at least one spring element for absorbing axial forces is arranged between the axial bearing and the shaft and / or between the axial bearing and the sleeve. The spring element does not necessarily border directly on the shaft or the axial bearing or the sleeve, but further elastic or non-elastic components can be arranged between the spring element and the shaft or between the spring element and the axial bearing or between the spring element and the sleeve.

[0008] A further advantage of the invention is that the bar material held by the bearing unit according to the invention can now rotate at higher speeds of at least 12,000 rpm without the bearing unit being damaged.

[0009] Preferably, the shaft is supported by two radial bearings that are axially spaced apart. A sleeve is preferably arranged between the inner rings of the two radial bearings, and a bushing is additionally arranged between the outer rings of the radial bearings to keep both radial bearings preloaded and to further ensure axial force transmission via the outer rings and the inner rings of the radial bearings.

[0010] The radial bearings are rolling bearings, particularly ball bearings. However, other types of rolling bearings, such as roller bearings or needle bearings, can also be used. The axial bearing is also a rolling bearing, particularly a ball bearing. Here, too, other rolling bearings, such as tapered roller bearings, could be used as alternatives.

[0011] Furthermore, it is preferably provided that the at least one radial bearing is arranged axially displaceably within the sleeve. For this purpose, a step is provided on the shaft, which rests against the inner ring of the radial bearing adjacent to the shaft exiting the sleeve. Furthermore, a further step is preferably provided on the shaft, by means of which the shaft is supported on the axial bearing.

[0012] The axial displacement of the shaft is only a few tenths of a millimeter to a few millimeters, depending on the design. Furthermore, axial displacement of the shaft only occurs when forces exceed a certain threshold. This threshold is preferably above 300 Newtons. The spring element is capable of absorbing forces of more than 500 Newtons. The forces absorbed by the spring element are preferably between 500 and 1000 Newtons, depending on the design of the spring element.

[0013] Preferably, the at least one radial bearing and the axial bearing are mounted within the sleeve from the side on which the shaft exits the sleeve and the bar stock to be machined is held. A receptacle is provided on the other side of the sleeve for connecting the bearing unit to a loading magazine of a machine tool. Short description of the drawings The Fig. 1 shows a section through a storage unit according to the invention for holding bar material. Description of preferred embodiments of the invention

[0014] The Fig. Figure 1 shows the basic structure of the bearing unit 10 according to the invention for holding bar stock. The bar stock is held by means of a clamping sleeve (not shown in the drawing). The clamping sleeve is pushed onto the free end of the shaft 12 and locked in place by means of a pin (not shown in the drawing). This pin for holding the clamping sleeve is guided into a hole 15 that extends through the shaft 12 perpendicular to the rotational axis 40 of the shaft 12.

[0015] A central bore 13 arranged in the direction of the axis of rotation 40 within the shaft 12 projects at least partially into the hole 15 for receiving the pin for holding the clamping sleeve. A radius pin 18 and a compression spring 17 are arranged within the central bore 13. A component 19 closes the end of the central bore 13 within the shaft 12. The pin for holding a clamping sleeve is in turn locked by the radius pin 18, which is movable in the axial direction, i.e. parallel to the direction of rotation 40, and which is subjected to an axial preload by means of the compression spring 17. This preload presses the radius pin 18 in the direction of the hole 15 located within the shaft 12 and, when the pin for holding the clamping sleeve is not mounted, partially into this hole 15 and thus presses against this very pin when the pin for holding a clamping sleeve is mounted.The compression spring 17 rests on the component 19 on its side opposite the radius pin 18. Since the central bore 13 within the shaft 12 does not fully penetrate into the hole 15, the radius pin 18, as shown in the drawing, only protrudes a short distance into the hole 15 and is pushed to the side when a pin for holding a clamping sleeve is inserted, thus exposing the hole 15.

[0016] The end of the shaft 12 that receives the clamping sleeve for holding the bar stock protrudes from the sleeve 14 on one side. The shaft 12 is rotatably mounted relative to the sleeve 14 by means of two radial bearings 20 and 22. A first radial bearing 20 is arranged within the sleeve 14 adjacent to the end of the shaft 12 protruding from the sleeve 14. A second radial bearing 22 is arranged within the sleeve 14 at a certain axial distance from the first radial bearing 20. The inner rings of both radial bearings 20, 22 are fastened to the shaft 12 by means of press fits P1 and P2.

[0017] Furthermore, an axial bearing 24 is provided within the sleeve 14 for absorbing axial forces, wherein the axial forces act predominantly on the end of the shaft 12 protruding from the sleeve 14 in the direction of the sleeve 14. The shaft 12 has a first step S1, by means of which it is supported on the inner ring of the first radial bearing 20. Furthermore, the shaft 12 has a second step S2, which acts as a contact surface on the axial bearing 24, i.e., the shaft 12 is supported on the axial bearing 24 with this contact surface.

[0018] The axial bearing 24 is arranged within the sleeve 14 between the step S2 of the shaft 12 on the one hand and a thrust bolt 30 on the other. The axial bearing 24 and the thrust bolt 30 are in turn arranged within a receptacle 36. The thrust bolt 30 is supported axially relative to the receptacle 36 on a threaded pin 32 which is screwed centrally within the receptacle 36. The receptacle 36 is arranged axially displaceably within the sleeve 14 and is supported on a spring element 34. The spring element 34 is preferably designed as a disc spring and is in turn supported on a threaded pin 38 screwed centrally within the sleeve 14. Both setscrews 32 and 38 are used to adjust the axial play of the axial bearing 24 and to adjust the preload of the spring element 34. Alternatively, the setscrew 32 can be omitted and, together with the thrust bolt 30, can be designed as a single piece with the holder 36.Likewise, the threaded pin 38 can be formed in one piece with the sleeve 14.

[0019] When a force acts on the end of the shaft 12 protruding from the sleeve 14 in the direction of the sleeve 14, the axial travel of the receptacle 36 arranged within the sleeve 14 is limited by a conical stop surface A, which is formed by a reduction in the inner diameter of the sleeve 14 and further ensures an emergency running property of the bearing unit 10 even with worn bearings.

[0020] A sleeve 26 is located between the inner rings of the first radial bearing 20 and the second radial bearing 22, which defines a minimum distance between the two inner rings. Furthermore, a bushing 28 is arranged between the outer ring of the first radial bearing 20 and the outer ring of the second radial bearing 22, which defines a minimum distance between the outer rings of the respective radial bearings 20 and 22.

[0021] The second radial bearing 22 is arranged adjacent to the axial bearing 24, wherein a distance is preferably provided as bearing clearance between the inner ring of the second radial bearing 22 and the axial bearing 24, while the outer ring of the second radial bearing 22 rests against the receptacle 36 without bearing clearance.

[0022] Axial forces acting on the end of the shaft 12 toward the sleeve 14 are transmitted through the second stage S2 of the shaft 12 to the axial bearing 24, which is spring-mounted relative to the sleeve 14 by means of the spring element 34, whereby these axial forces are largely absorbed by the spring element 34. Through the first stage S1 of the shaft 12, axial forces are further transmitted to the radial bearings 20 and 22. The sleeve 26 arranged between the inner rings of both radial bearings 20 and 22 and the bushing 28 arranged between the outer rings of both radial bearings 20 and 22 also serve to transmit forces between the radial bearings 20 and 22 and further serve to transmit forces to the receptacle 36.

[0023] To hold the first radial bearing 20 and to close the sleeve 14 on the side on which the shaft 12 leaves the sleeve 14, a cover 16 is provided which is pressed into the sleeve 14 and is alternatively or additionally glued or (laser-) welded.

[0024] Preferably, there is an axially through opening in the sleeve 14 so that both threaded pins 32 and 38 can be adjusted from the side of the sleeve 14 opposite the exit of the shaft 12 even after the radial bearings 20 and 22 and the axial bearing 24 have been mounted within the sleeve 14. List of reference symbols 10 storage units 12 Wave 13 centric bore 14 sleeve 15 holes 16 Cover 17 compression spring 18 radius pin 19 Component 20 first radial bearing 22 second radial bearing 24 thrust bearings 26 sleeve 28 socket 30 pressure bolts 32 first threaded pin 34 spring element 36 recording 38 second threaded pin 40 axis of rotation S1 first stage of the wave S2 second stage of the wave P1 Press fit of the first radial bearing P2 Press fit of the second radial bearing A stop

Claims

[1] Bearing unit (10) for receiving bar stock, comprising a shaft (12) and a sleeve (14), wherein the shaft (12) is mounted within the sleeve (14) by means of at least one radial bearing (20, 22) and is supported on an axial bearing (24), wherein the at least one radial bearing (20, 22) has an inner ring and an outer ring, wherein the shaft (12) is arranged axially displaceably within the sleeve (14), and wherein at least one spring element (34) for absorbing axial forces is arranged between the axial bearing (24) and the shaft (12) and / or between the axial bearing (24) and the sleeve (14), characterized by that the shaft (12) has a first step (S1) by means of which the shaft (12) is supported on the inner ring of the first radial bearing (20) and / or that the shaft (12) has a second step (S2) which serves as a contact surface and by means of which the shaft (12) is supported on the axial bearing (24). [2] Bearing unit (10) according to claim 1, characterized by that the at least one radial bearing (20, 22) is arranged axially displaceably within the sleeve (14). [3] Bearing unit (10) according to one of the preceding claims, characterized by that two radial bearings (20, 22) are provided for supporting the shaft (12) within the sleeve (14). [4] Bearing unit (10) according to the preceding claim, characterized by that a bushing (28) is arranged between the outer rings of the two radial bearings (20, 22), on which the outer rings are supported. [5] Bearing unit (10) according to claim 3, characterized by that a sleeve (26) is arranged between the inner rings of the two radial bearings (20, 22), on which the inner rings are supported. [6] Bearing unit (10) according to one of the preceding claims, characterized by that the spring element (34) is arranged between the sleeve (14) and that side of the axial bearing (24) which is opposite the contact surface of the shaft (12).

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