Machine tool in column design

Abstract

A machine tool (10) of column design, in particular a pillar drilling machine, comprising: a. a column (12) attached to a base plate (14), b. a bearing bridge (18) for a working tool (22), which is mounted to be displaceable in the axial direction of the column (12), c. a return spring (44) which acts on the bearing bridge (18) and is arranged between the bearing bridge (18) and an associated stop element (46), d. wherein the stop element (46) is adjustable on the column (12) in its axial direction and can be fixed by means of a clamping lever (50), e. wherein a complete machine head (24) is arranged on the bearing bridge (18) as a working tool (22), f. a rack (34) arranged on the column (12) which engages with a gear (38) associated with the bearing bridge (18), whereby the bearing bridge (18) is displaceable along the column (12), characterized in thata raised section (64) is provided on one of the toothless end sections (60) of the rack (34) facing the base plate (14) as a locking element (62) for the stop element (46) in order to prevent the bearing bridge (18) from slipping out of the rack (34), and that the raised section (64) is formed with an angle (74) with a short leg (76) and a long leg (78), wherein the short leg (76) bears at least partially against an end face (80) and the long leg (78) bears at least partially against the toothless end section (60) of the rack (34).

Description

State of the art The present invention relates to a machine tool of pillar design, in particular a pillar drilling machine, with a column attached to a base plate, on which a bearing bridge for a working tool is slidably mounted in the axial direction of the column, wherein the bearing bridge is acted upon by a return spring which is arranged in the area between the bearing bridge and an associated stop element which is adjustable on the column in its axial direction and can be fixed in a predetermined operating position by means of a clamping lever, and wherein a complete machine head is arranged on the bearing bridge as a working tool, which contains a drive motor with gearbox in a housing and has a tool holder. From DE 10 2010 042 951 A1, such a machine tool designed in the manner of a pillar drill is known, in which a working device, in particular a drilling machine, is attached to a bearing bridge as a complete machine head, which is moved downwards or upwards on an associated column when machining a workpiece and when lifting in the opposite direction. A disadvantage of this state of the art is that if the bearing bridge is displaced too far axially towards a base plate or a workpiece being machined, this engagement with the rack is lost, and the bearing bridge and machine head lower themselves uncontrollably or slide completely down the column. This lowering of the machine head onto the base plate with the workpiece resting on it, which cannot be easily remedied by the user, can compromise workplace safety and potentially damage the tooling and / or the workpiece. Disclosure of the invention One object of the invention is therefore to provide a new machine tool in a pedestal design in which an unwanted and uncontrolled lowering of an associated machine head can be safely and reliably prevented. This problem is solved by a pillar-type machine tool, in particular a pillar drill, with a column attached to a base plate. A bearing bridge for a working tool is mounted on this column so as to be axially displaceable. The bearing bridge is acted upon by a return spring located between the bearing bridge and an associated stop element. This stop element is adjustable along the column in its axial direction and can be locked in a predetermined operating position by means of a clamping lever. A complete machine head, comprising a drive motor with gearbox and a tool holder, is mounted on the bearing bridge as the working tool. A locking element is provided to limit the movement of the bearing bridge towards the base plate. The invention thus enables the provision of a structurally simple lower end stop or end stop for the column-type machine tool, reliably preventing unwanted and uncontrolled lowering of the bearing bridge with the attached machine head when the lower end of the axial displacement travel on the column is reached. This avoids any impairment of workplace safety or damage to the tooling and / or the workpiece being machined. Preferably, a rack is arranged on the column in the axial direction, which engages with a gear associated with the bearing bridge, wherein the bearing bridge can be displaced along the column by rotating the gear using a rotary element, in particular a handwheel. This allows for smooth and precise adjustment of the vertical working position of the bearing bridge, and thus of the machine head, along the column in relation to the base plate or the workpiece being machined. Due to the reduction action of the rack and pinion drive, a comparatively high axial force can be exerted on the tooling with minimal manual effort from the user, directed towards the workpiece. According to a first embodiment, a raised section is provided on one of the toothless end sections of the rack facing the base plate as a blocking element for the stop element in order to prevent the bearing bridge with the machine head attached to it from slipping out of the rack. This results in a particularly simple and constructive implementation of the blocking element. Preferably, the height of the end section and the material thickness of the extension together are greater than the total height of the rack. This reliably prevents the raised section from overflowing through the stop element. The end section of the rack and the riser are preferably attached to the column by means of a fastening element. This allows the extension and the end section of the rack to be attached to the column with only one fastening element, thereby reducing manufacturing effort and material usage. Preferably, the elevation is formed with an angle with a short and a long leg, wherein the short leg rests at least partially on an end face and the long leg rests at least partially on the toothless end section of the rack. This ensures that the raised section is securely fixed against rotation on the rack. Furthermore, compared to an integral design with the rack, the raised section can be manufactured using less material. Alternatively, the raised section can also be formed, for example, by a fastening element that is taller than the overall height of the rack. Preferably, a stop surface for the blocking element is formed on the stop member, directed towards the base plate. This allows for precise definition of the stop geometry with which the stop element engages the blocking element. If necessary, the stop surface can be provided with a damping element, at least in part, to improve ease of use. The damping element can, for example, be made of an elastomer. According to a second embodiment, a longitudinal groove is provided in the rack at least in sections, in which a projection formed on the stop member and pointing towards the column is longitudinally displaceable as a locking element for the stop member in order to prevent the bearing bridge with the machine head arranged on it from slipping out of the rack. This ensures engagement between the gear and the rack under all operating conditions of the machine tool. The longitudinal groove preferably runs centrally with respect to the transverse extent of the rack, meaning that the distances on both sides of the central longitudinal groove to the longitudinal edges of the rack are approximately equal. Preferably, the longitudinal groove extends to a toothless end section of the rack facing the base plate. This provides an axial travel limit for the projection guided in the longitudinal groove, at least in the direction of the base plate. The tooth clearance of the end section increases its mechanical load-bearing capacity and simplifies its attachment to the column. The end section of the rack is preferably attached to the column by means of a fastening element, and the height of the end section is less than or equal to the total height of the rack. This allows the height of the end section to be dimensioned so that a flush finish of the fastening element with the toothing of the rack is possible, e.g. by creating a countersink for the fastening element. Preferably, the height of the projection of the stop element is less than or equal to the depth of the longitudinal groove. This ensures reliable longitudinal guidance of the projection in the longitudinal groove without significantly impairing the mechanical load-bearing capacity of the rack. To simplify manufacturing, the depth of the longitudinal groove preferably corresponds approximately to the tooth height of the rack. Furthermore, the width of the projection is slightly smaller than the groove width of the longitudinal groove to guarantee the smoothest possible, yet ideally backlash-free, movement of the bearing bridge along the rack. Brief description of the drawings The invention is explained in more detail below with reference to exemplary embodiments shown in the drawings. The drawings show: Fig. 1 a perspective front view of a machining tool according to the invention, Fig. 2 a rear view of the machining tool of Fig. 1, Fig. 3 a longitudinal section through the machining tool of Fig. 1, with a first embodiment of a locking element, Fig. 4 an enlarged view of a detail IV of Fig. 3, Fig. 5 a partial longitudinal section through a column associated with the machining tool of Fig. 1, with a stop element and a rack according to a second embodiment of a locking element, and Fig. 6 an enlarged perspective view of an end section of the rack facing the workpiece in Fig. 5. Description of the exemplary implementations Figures 1 and 2 show an exemplary machine tool 10 in a pillar design, which here is configured as a pillar drilling machine. However, it should be noted that the present invention is not limited to pillar drilling machines, but can also be applied to other pillar machine tools, such as a pillar milling machine or a pillar combination machine that enables drilling and / or milling. The processing machine 10 is designed specifically for use in DIY projects, but can also be used in industrial settings. For illustrative purposes, it features a hollow cylindrical column 12, which is vertically oriented in the operating position of the processing machine 10. The lower end of the column 12 is detachably attached to a base plate 14, for example by means of a clamp 16, and forms a right angle with the base plate 14. A bearing bridge 18 is mounted on the column 12 so that it is axially displaceable along the column 12, i.e., longitudinally displaceable, as indicated by arrow 20. A working device 22 is attached to the bearing bridge 18. This device is exemplified as a complete machine head 24, which is longitudinally displaceable along the column 12 in the direction of arrow 20, together with the bearing bridge 18. The exemplary machine head 24 has a housing 26, a drive motor with gearbox (not shown), and a tool holder 28, which is equipped with a chuck 30 in which, for illustrative purposes, a tool 32, e.g., a drill bit, is clamped. A rack 34 is attached to or formed on the column 12, running approximately parallel to a longitudinal center axis 36 of the column 12. A gear 38 or pinion engages with the rack 34 and is non-rotatably connected to a shaft 40, which is rotatably mounted together with the shaft in the bearing bridge 18. A manually operated rotary element 42, e.g., in the form of a rotary knob or handwheel, is non-rotatably connected to the shaft 40. Every rotary movement of the gear 38 engaging with the rack 34 is transformed into a vertical movement of the bearing bridge 18 together with the machine head 24, whereby the machine head 24 can be moved in the direction of arrow 20 both downwards in a working direction towards the base plate 14 and in the opposite direction, without any relative movement of parts of the machine head 24 to each other. The bearing bridge 18 is acted upon by a return spring 44, which here is designed as a compression spring, in particular as a relatively strong cylindrical helical spring, that coaxially surrounds the column 12 at a small radial distance. The return spring 44 is supported at one end on the bearing bridge 18, while the other end of the return spring 44 is supported on a stop element 46 that is axially spaced from the rotary element 42. This stop element is adjustable in the axial direction of the column 12 and, via the return spring 44, bears the weight of the bearing bridge 18 with the machine head 24. The latter is forced into a rest position shown in Fig. 1 by a predetermined spring force applied by the return spring 44, in which the bearing bridge 18, or by way of example a lower section thereof, rests axially against the stop element 46 on its underside.By adjusting the stop element 46 by longitudinal displacement on the column 12, the machine head 24 can be set to an application-specific operating position in which the tip of the insert tool 32 is located either in the vertical position shown or in a lower or higher position before work begins. To set the application-specific operating position of the machine head 24, the fixed connection of the stop element 46 to the column 12 must be released. After reaching the application-specific operating position, the stop element 46 is again fixedly connected to the column 12. This is achieved by the stop element 46 having, among other things, a slotted clamping bracket 48, which can be clamped radially with respect to the column 12 by means of a pivotable clamping lever 50 and thus positively locked onto it. The clamping bracket 48 incorporates, among other things, a clamping lever shaft 52 for supporting the clamping lever 50, and the clamping bracket 48, due to its slotted design, has two legs 54, 56. Another clamping lever, not marked with a reference numeral, serves to set a depth stop. Fig. 3 shows the bearing bridge 18 of the machine tool 10 from Figs. 1 and 2, which is mounted longitudinally displaceably on the (illustratively foreshortened) column 12. For the sake of simplicity and clarity, the machine head 24 of the machine tool 10 from Fig. 1 has been omitted. The column 12 is detachably attached to the base plate 14 at its lower end, preferably forming a right angle with it. The bearing bridge 18 is forced into the vertical rest position shown by the return spring 44, which is supported between the upper end of the bearing bridge 18 and the stop element 46. The gear 38 or pinion, which is rotatably mounted on the bearing bridge 18, is in permanent engagement with the rack 34, so that the bearing bridge 18 can be moved on the column 12 in both directions of the arrow 20 by rotating the gear 38.In this process, the bearing bridge 18 is displaced towards the base plate 14 against the force of the return spring 44, whereas a displacement of the bearing bridge 18 in the opposite direction is supported by the force of the return spring 44. With the clamping lever 50 sufficiently loosened, the stop element 46 itself is also displaceable in both directions of arrow 20 on the column 12 and can be fixed to it by tightening the clamping lever 50. A locking element 62 is provided at an end section 60 of the rack 34 facing the workpiece or the base plate 14. In its first embodiment shown here, this locking element is designed as an angled projection 64 and is preferably attached to the column 12 together with the rack 34 by means of only one fastening element 66. The rack 34 is also shown here, by way of example, attached to the column 12 by means of two further similar fastening elements 68, 70. The three fastening elements 66 to 70, which are preferably arranged at equal intervals from one another, can be formed, for example, with socket head cap screws or the like. A stop surface 72, formed on the underside of the stop member 18 and pointing towards the base plate 14, serves as a defined stop geometry for the locking member 62. This stop surface 72, as part of the stop member 46, has an exemplary, at least approximately, quarter-circle cross-sectional contour. The locking member 62 reliably prevents the bearing bridge 18 or the stop member 46 from being moved too far towards the base plate 14 by a user, thereby preventing the permanent engagement between the rack 34 and the gear 38 from being lost and / or the machine head 24 of Fig. 1 from being lowered completely down to the base plate 14. Fig. 4 shows an enlarged view of section IV of Fig. 3. In this section, the raised portion 64 is arranged in the area of ​​the toothless end section 60 of the rack 34 as an end stop or lower end stop for the bearing bridge. The raised portion 64 is preferably formed with an angle 74, which has a short and a long leg 76, 78, wherein the short leg 76 preferably rests fully against an end face 80 of the rack 34 and the legs 76, 78 are formed approximately at right angles to each other. For the mechanical fastening of the raised portion 64 or the angle 74, a dotted opening 82, e.g., a preferably countersunk bore, is preferably provided in the long leg 78 for the fastening element 66, also indicated by a dotted line, which serves to fasten the angle 74 and the rack 34 to the column 12. The height 84 of the toothless end section 60 of the rack 34 and the material thickness 86 of the long leg 78 of the angle 74 or the rise 64 are preferably together greater than the total height 88 of the rack 34. This reliably prevents the rise 64 from overshooting. The tooth height 90 of the rack 34 is preferably dimensioned such that it corresponds to approximately half the total height 88 of the rack 34. This ensures reliable engagement between the gear and the rack 34 while maintaining a sufficiently high residual mechanical load-bearing capacity of the rack 34. Furthermore, the height 84 of the end section 60 preferably corresponds at least approximately to the overall height 88 of the rack 34, thus simplifying the manufacturing of the rack 34. A length 92 of the short leg 76 is preferably less than or equal to the height 84 of the end section 60 of the rack 34, and a length 94 of the long leg 78 is preferably less than or equal to a length 96 of the toothless end section 60 of the rack 34. The lengths 92 and 94 are each defined outside a manufacturing-related radius 98 between the legs 76 and 88. Fig. 5 shows a simplified section of the machining tool 10 from Fig. 1, with the stop element 46 mounted longitudinally displaceably on the column 12 and the bearing bridge 18, as well as a rack 100 and a locking element 106 according to a second embodiment. The rack 100 preferably has an opening 102, e.g., a bore, into which a suitable fastening element, such as a socket head cap screw or the like, can be inserted to fasten the rack 100 to the column 12. In contrast to the rack 34 of Fig. 1, Fig. 2, Fig. 3 to Fig. 4, the rack 100 has at least a section of a longitudinal groove 104 with a preferably at least approximately rectangular cross-sectional geometry. The stop member 46 is provided with the locking member 106, which is preferably formed with a projection 108 pointing towards the rack 100 or the column 12, preferably at least substantially cuboid in shape, which engages at least partially in a form-fitting manner in the longitudinal groove 104. Otherwise, the construction and function of the rack 100 correspond to that of the rack 34 of Figs. 1, 2, 3 to 4. A depth 110 of the longitudinal groove 104 preferably corresponds at least approximately to a height 112 of the toothing or teeth of the rack 100 – of which only one tooth 114 is provided with a reference numeral to represent all the others – or to a height 116 of the projection 108 on the stop member 46. A width 118 of the projection 108 preferably corresponds to the width of the longitudinal groove 104 (not specified here) (see Fig. 6). The necessary fit between the projection 108 and the longitudinal groove 104 is designed such that the smooth yet largely backlash-free movement of the stop member 46 in the axial direction with respect to the column 12 is maintained. Fig. 6 shows an enlarged view of a toothless end section 120 of the rack 100 from Fig. 5. This section has, for illustrative purposes, a dotted opening 122, e.g., a bore, into which a fastening element 124, also indicated by dots, such as a socket head cap screw or the like, is inserted to fasten the end section 120 of the rack 100 to the column 12. To achieve a flush finish between the fastening element 124 and the toothless end section 120, the opening 122 may have a countersink. The toothless end section 120 points towards the base plate 14 of the machine tool 10 from Figs. 1 and 2. A shallow, pocket-shaped recess 126 is incorporated into the end section 120, serving as an end stop for the cuboid projection of the stop member 46. The projection 108 is at least partially positively engaged in the receptacle 126 when the stop member 46 comes to rest against the end section 120. The toothless end section 120, therefore, acts in conjunction with the pocket-shaped recess 126 as an end stop for the stop member 46 and the bearing bridge 18 of Figures 1 and 2 with the attached machine head 24 of Figures 1 and 2. The height 128 of the toothless end section 120 is preferably less than or equal to the overall height 130 of the rack 100, in order to enable material-saving manufacturing, particularly in the case of machining of the rack 100. The width 132 of the longitudinal groove 104 of the rack 100 preferably corresponds approximately to the width of the projection 118 and at the same time preferably to about one-third of the overall width 134 of the rack 100. The longitudinal groove 104 preferably runs centrally in the longitudinal direction of the rack 100, creating two parallel rows of teeth 136, 138, which are separated from each other by the longitudinal groove 104 running centrally between them. Deviating dimensions of the longitudinal groove 104 and of the two rows of teeth 136, 138 – with corresponding adjustment of the geometric shape of the cuboid projection 108 of Fig. 5 – are also possible.

Claims

A machine tool (10) of column design, in particular a pillar drilling machine, comprising: a. a column (12) attached to a base plate (14), b. a bearing bridge (18) for a working tool (22), which is mounted to be displaceable in the axial direction of the column (12), c. a return spring (44) which acts on the bearing bridge (18) and is arranged between the bearing bridge (18) and an associated stop element (46), d. wherein the stop element (46) is adjustable on the column (12) in its axial direction and can be fixed by means of a clamping lever (50), e. wherein a complete machine head (24) is arranged on the bearing bridge (18) as a working tool (22), f. a rack (34) arranged on the column (12), which engages with a gear (38) associated with the bearing bridge (18), whereby the bearing bridge (18) is displaceable along the column (12), characterized in thata raised section (64) is provided on one of the toothless end sections (60) of the rack (34) facing the base plate (14) as a locking element (62) for the stop element (46) in order to prevent the bearing bridge (18) from slipping out of the rack (34), and that the raised section (64) is formed with an angle (74) with a short leg (76) and a long leg (78), wherein the short leg (76) bears at least partially against an end face (80) and the long leg (78) bears at least partially against the toothless end section (60) of the rack (34). Machining machine according to claim 1, characterized in that a height (84) of the end section and a material thickness (86) of the elevation (64) together are greater than a total height (88) of the rack (34). Machining machine according to claim 1 or 2, characterized in that the end section (60) of the rack (34) and the elevation (64) are attached to the column (14) by means of a fastening element (66). Machining machine according to one of claims 1 to 3, characterized in that a stop surface (72) directed towards the base plate (14) for the blocking element (62) is formed on the stop member (46). Machining machine according to claim 1, characterized in that a longitudinal groove (104) is provided in the rack (100) at least partially, in which a projection (108) formed on the stop member (46) and pointing towards the column (12) is longitudinally displaceable as a locking element for the stop member (46) in order to prevent the bearing bridge (18) with the machine head (24) arranged thereon from slipping out of the rack (100). Machining machine according to claim 5, characterized in that the longitudinal groove (104) extends to a toothless end section (120) of the rack (100) facing the base plate (14). Machining machine according to claim 5 or 6, characterized in that the end section (120) of the rack (100) is attached to the column (12) by means of a fastening element (124) and a height (128) of the end section (120) is less than or equal to a total height (130) of the rack (100). Machining machine according to one of claims 5 to 7, characterized in that a height (116) of the projection (108) of the stop member (46) is less than or equal to a depth (110) of the longitudinal groove (104).

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