Ram clamping system

Abstract

A ram clamping system (100) is provided with a rotationally symmetrical base body (110) which has an opening which passes through the rotationally symmetrical base body (110) along its axis of symmetry and in which opening a draw rod (140) runs, with a collet chuck (120) which can be clamped by means of the draw rod (140) for fixing a ram (190) belonging to the ram clamping system (100), and with an exchangeable holder (180), the interior (181) of which the ram (190) passes through before entering the collet chuck (120), in which at least a section of the collet chuck (120) projects beyond the end face of the base body (110), on which the exchangeable holder (180) is arranged, in the direction of extension of the draw rod (140) and enters the interior (181) of the exchangeable holder (180).

Description

Machine tools are operated in an automated manner to an ever greater extent. This has the particular consequence that the tool change is also carried out partially or fully automatically during the operation of such a machine tool. It is common practice to connect the various tools to a spindle, an axis of rotation or another dividing apparatus of the machine tool via a tool holder.There are also cases in which the workpiece to be machined is coupled to the spindle, the axis of rotation or the other partial apparatus of the machine tool. In order to clarify this, the term "tool or workpiece holder" is used below, although actually each tool holder is in principle also a workpiece holder or becomes a workpiece holder, if the clamping means into which the tool is received as intended during a tool holder is used for holding a workpiece.It is known to fasten tools or workpieces, which have an axial hole, in the tool or workpiece holder by means of a clamping ram, which has in particular an elongated cylindrical shank with a collar, which in particular forms a radial thickening, at one end. For this purpose, the clamping ram is guided through the hole and the cylindrical shank of the clamping ram is held in a chuck which is usually arranged in the interior of a base body of the ram clamping system and is retracted in the axial direction to such an extent that the tool or workpiece bears against a contact surface of a holder which is in many cases specific to the tool or workpiece and is therefore usually arranged exchangeably on the end side of the ram clamping system and is held clamped between the contact surface and the collar of the clamping ram.An example of such a system is disclosed in DE 10 2016 125 269 B4. It describes a clamping or gripping device comprising a base body, an elastic expansion sleeve which is provided at the front axial end region of the base body and a clamping element which is held in a passage channel of the base body in an axially movable manner and passes through the expansion sleeve, wherein an outer cone of the clamping element interacts with an inner cone of the expansion sleeve in order to expand it radially elastically when the clamping element is moved axially to the rear. A pressure chamber filled with hydraulic medium is formed in the base body, which is positioned such that the clamping element is moved axially rearward by a pressure increase in the pressure chamberA problem of known plunger clamping systems is that their holding torque suffers from the high torsion of the plunger because of the considerable length of the plunger. The object of the invention is therefore to provide a plunger clamping system with an improved holding torque. This object is achieved by a plunger clamping system having the features of claim 1.The plunger clamping system according to the invention has a rotationally symmetrical main body with an opening which passes through the rotationally symmetrical main body along its axis of symmetry and in which a pull rod runs. In addition, it has a collet chuck that can be clamped by means of the pull rod for fixing a plunger belonging to the plunger clamping system and an exchangeable holder, the interior of which the plunger passes through before entering the collet chuck. It should be noted here that both holders and plungers are optionally matched to the respective workpiece geometry and therefore represent replaceable parts. A plunger clamping system can therefore also include a plurality of holders and / or a plurality of plungers, of which however only one holder and one plunger are always used for operation.It is essential to the invention that at least a portion of the collet projects beyond the end face of the base body on which the replaceable holder is arranged in the direction of extension of the pull rod and enters the interior of the replaceable holder. In this way, it becomes possible to use substantially shorter plungers than previously customary, the torsion of which is lower because of their shorter length, so that it becomes possible to operate with higher holding torques.In a particularly preferred embodiment of the invention, the clamping legs of the collet comprise a recess which is located behind the clamping jaws in the axial direction and in which an ejector for the plunger is received. This ejector can be designed as a mandrel present in the front region of the pull rod and allows plungers with a head countersunk in the tool or workpiece during machining of the workpiece to be pushed out of the counterbore when releasing the collet for changing the tool or workpiece, so that they can be gripped more easily by an operator or a robot.While in principle an interaction of the clamping jaws of the clamping tongs with the wall surfaces of the opening passing through the base body can be used when pulling the clamping jaws into the opening in order to bring about the desired clamping effect of the clamping jaws on the plunger, in a preferred embodiment of the invention the plunger clamping system has a clamping tongs receptacle which projects beyond the end face of the base body on which the replaceable holder is arranged in the direction of extension of the pull rod and enters the interior space of the replaceable holder. If clamping jaws of the clamping jaws tapering in the direction of tension are drawn into the clamping jaw receptacle, a clamping effect of the inner sides of the clamping jaws inward with the plunger and a clamping effect of the outer sides of the clamping jaws with the clamping jaw receptacle results which is advantageous for the achievable positioning accuracy.It is particularly advantageous for achieving this effect if the walls of the collet holder have slits or groove-shaped weakenings.It has a particularly advantageous effect on the achievable positioning accuracy if the collet holder is tensioned within the base body in the axial direction by a helical spring and is tensioned in the direction of the spread by a disk spring.The plunger clamping system can be operated particularly easily by means of a machine tool if the pull rod has a tightening bolt or a pull rod adapter at its end opposite the collet chuck for connection to a spindle clamping system of a machine tool.In a preferred embodiment of the invention, the collet is also detachably connected to the pull rod and arranged on the base body in such a way that after the connection to the pull rod has been released, the collet is removable from the base body in the direction opposite to the insertion direction of the plunger into the collet. In this way, it is possible to easily replace the clamping tongs when they are worn out or have a defect, and to use clamping tongs with different diameters, so that, for example for workpieces with a larger bore where high machining forces act, the plunger clamping / pulling diameter can be increased, thereby pulling with a higher force and clamping the workpiece more strongly.This can be realized very easily, for example, by connecting the collet chuck to the pull rod via a screw connection. An alternative possibility to this is that the collet is connected to the pull rod via a bayonet connection.In order to facilitate the insertion and extraction of the collet, it is helpful if the clamping jaws of the collet have openings on their end face pointing away from the pull rod for receiving a tool for releasing the connection between the collet and the pull rod and / or for extracting the collet from the base body. Such a tool can also be part of the plunger clamping system as a separate part.The invention is explained in more detail below with reference to figures which show exemplary embodiments. It shows: FIG. 1 : an isometric view of a plunger clamping system with a clamped workpiece; FIG. 2 : an isometric view of the plunger clamping system from FIG. 1 with the plunger and holder removed; FIG. 3 : a sectional view of the ram clamping system with the workpiece from FIG. 1 clamped; and FIG. 4 : a sectional view of the plunger clamping system with the plunger and holder from FIG. 2 removed.FIG. 1 shows an isometric view of a plunger clamping system 100 with clamped workpiece 1, It is possible to see the base body 110 of the plunger clamping system, on the end face of which-in the present example with four screws 111 facing the observer-a workpiece-specific holder 180 is arranged, but other alternatives, such as a quick-change system, for example. At the end of the holder facing the observer, a contact surface for the workpiece 1 is arranged which is concealed in FIG. 1 by the workpiece 1 resting against it and which is fixed by a plunger 190 which passes through an opening in the workpiece 1 in such a way that its plunger head 191 is recessed in the workpiece 1, on the contact surface of the holder 180 formed by the end surface of the holder 180 facing the workpiece 1.At the end of the base body facing away from the observer, a tightening bolt or tie rod adapter 170 can be seen, via which the actuation of the plunger clamping system 100 takes place by a machine tool on which it is installed. The function of the plunger clamping system 100 in such an actuation is explained in detail further belowIn the illustration according to FIG. 2, the plunger clamping system 100 is depicted with the holder 180 removed, such that the collet 120 projecting beyond the end face of the base body 110 and its collet receptacle 130 likewise projecting beyond the end face of the base body 110 are visible, which in this exemplary embodiment has slots 131. Accordingly, when the holder 180 is installed, the collet 120 and the collet holder 130 are at least partially accommodated in the interior 181 of the holder 180 visible in FIG. 4 ; however, they also each have, at least in the exemplary embodiment shown, sections which are arranged in the base body 110, as FIGS. 3 and 4 show.It can also be clearly seen in FIG. 2 that the clamping jaws 122, which are arranged at the end of the clamping legs 121 of the collet chuck 120 facing the workpiece 1, have openings 123 on their end side, which is covered by the pull rod 140 that is hidden from the base body 110 in the illustration of FIG. 2 but which points away from the pull rod 140 that is visible in FIGS. 3 and 4, for receiving a tool for releasing the connection between the collet chuck 120 and the pull rod 140 and / or for pulling out or pushing in the collet chuck 120 from the base body 110.Further details regarding the structure of the plunger clamping system 100 and regarding its mode of operation can be found in the sectional views according to FIGS. 3 and 4. This illustration shows the position in the opening 112 which passes through the base body 110 along its axis of symmetry which coincides with the central axis of the rotationally symmetrical base body 110 about which the rotation takes place when the plunger clamping system 100 is used.A pull rod 140 is arranged in the interior of the opening 112, which pull rod is connected at its end opposite the collet 120 to the tightening bolt or pull rod adapter 170, via which the actuation of the plunger clamping system 100 takes place by a machine tool on which it is installed. Starting from the other end of the pull rod 140, a concentric bore leads into the interior of the pull rod 140, the end of which bore has a means for the detachable connection to the collet chuck 120 on the side facing the workpiece 1. In the example shown, this is an internal thread into which the collet 120 is screwed with an external thread arranged at the end of the clamping legs 121 opposite the clamping jaws 122.In addition, an ejector 141 with an extension 142 is arranged axially displaceably in the interior of this bore, wherein, however, the displacement in the direction of the workpiece 1 is limited by a stop 143 firmly connected to the pull rod 140. The extension 142 engages in recesses which are provided in the clamping legs 121 of the clamping jaw 120 lying behind the clamping jaws 122 in the axial direction. The ejector 141 is supported at its bottom opposite to the workpiece 1 by a spring 144.As can be seen particularly well in FIG. 3, one section of the clamping legs 121 is accommodated within the base body 110 of the plunger clamping system 100, while another section of the clamping legs 121 (and thus of the collet 120) including the clamping jaws 122 projects beyond the end face of the base body 110 facing the workpiece 1 and, as shown in FIG. 4, is accommodated in the interior 181 of the holder 180.Likewise protruding into the interior 181 of the holder 180 is the collet receiver 130, the section 135 of which running within the base body 110 is supported by means of a helical spring 132 on a base piece 133 which is in turn mounted on a disc spring 134, as a result of which the collet receiver 130 is tensioned within the base body 110 in the axial direction by the helical spring 132 and is tensioned in the direction of the spread upon actuation of the pull rod 140 by the disc spring 134.In order to clamp a workpiece 1 or tool with the plunger clamping system 100, it is threaded onto the plunger 190, the plunger head 191 of which can produce a positive fit with the workpiece or tool, and the end of the plunger 190 opposite the plunger head 191 is inserted between the clamping jaws 122 of the collet 120, so that the workpiece 1 comes to rest against the contact surface formed by the end face of the holder 180 facing it.By pulling on the tightening bolt or tie rod adapter 170, the tie rod 140 is subsequently pulled back against the resistance of the compression spring 145, which at the same time leads to the clamping legs 121 of the clamping collet 120 being pulled back. This leads to a clamping effect of the collet 120 on the plunger 190 because of the interaction of the clamping jaws 122, the outer diameter of which increases in the direction of the workpiece 1, with the inner diameter of the collet receptacle 130, which decreases counter to this direction. Accordingly, the plunger 190 is gripped and pulled in the direction of the end of the base body 110, whereby the ejector 141 is pushed back counter to the force of the spring 144 and the workpiece 1 is pulled against the contact surface. In this case, a high positioning accuracy is maintained, in particular because of the slots 131 or weakenings of the collet chuck receptacle 130 and the mounting or tensioning thereof by the helical spring 132 and the disk spring 134. If the tension on the pull rod 140 is no longer maintained, the compression spring 145 presses the pull rod 140 forward again. Accordingly, the collet 120 slides forward in the collet receiver 130, the plunger 190 is no longer clamped by the jaws 122, and the spring 144 can relax, thereby expelling the plunger 190 and now being easily grasped.List of reference characters1 Workpiece 100 Plunger clamping system 110 Base body 111 Screw 112 Opening 120 Collet 121 Clamping limb 122 Clamping jaw 123 Opening 130 Collet receptacle 131 Slot 132 Helical spring 133 Base piece 134 Cup spring 135 Section 140 Pull rod 141 Ejector 142 Extension 143 Stop 144 Spring 145 Compression spring 170 Tightening bolt or pull rod adapter 180 Holder 181 Interior 190 Plunger 191 Plunger head

Claims

Plunger clamping system (100) having a rotationally symmetrical main body (110) which has an opening passing through the rotationally symmetrical main body (110) along its axis of symmetry, in which opening a pull rod (140) runs, having a collet (120) which can be clamped by means of the pull rod (140) for fixing a plunger (190) belonging to the plunger clamping system (100), and having an exchangeable holder (180), the interior (181) of which the plunger (190) passes through before entering the collet (120), characterized in that at least one section of the collet (120) projects beyond the end face of the main body (110), on which the exchangeable holder (180) is arranged, in the direction of extension of the pull rod (140) and enters the interior (181) of the exchangeable holder (180).The plunger clamping system (100) according to claim 1, characterized in that the clamping legs (121) of the collet chuck (120) have a recess which is located behind the clamping jaws (122) in the axial direction and in which an ejector (141) for the plunger (190) is accommodated.The plunger clamping system (100) according to any one of claims 1 or 2, characterized in that the plunger clamping system (100) has a collet holder (130), which projects beyond the end face of the base body (110), on which the replaceable holder (180) is arranged, in the direction of extension of the pull rod (140) and enters the interior space (181) of the replaceable holder (180).Plunger clamping system (100) according to Claim 3, characterized in that the walls of the collet holder (130) have slots (131) or groove-shaped weakenings.Plunger clamping system (100) according to either of Claims 3 and 4, characterized in that the collet chuck receptacle (130) is tensioned within the base body (110) in the axial direction by a helical spring (132) and is tensioned in the direction of the spread by a disc spring (134).Plunger clamping system (100) according to one of Claims 1 to 5, characterized in that the pull rod (140) has, at its end opposite the collet (120), a tightening bolt or pull rod adapter (170) for connection to a spindle clamping system of a machine tool.The plunger clamping system (100) according to any one of claims 1 to 6, characterized in that the collet (120) is detachably connected to the pull rod (140) and is arranged on the base body (110) in such a way that the collet (120), after the connection to the pull rod (140) has been released, can be removed from the base body (110) in the direction opposite to the insertion direction of the plunger (190) into the collet (120).Plunger clamping system (100) according to Claim 7, characterized in that the collet (120) is connected to the pull rod (140) via a screw connection.Plunger clamping system (100) according to claim 7, characterised in that the collet (120) is connected to the pull rod (140) via a bayonet connection.Plunger clamping system (100) according to one of Claims 7 to 9, characterized in that the clamping jaws (122) of the collet (120) have, on their end side pointing away from the pull rod (140), openings (123) for receiving a tool for releasing the connection between the collet (120) and the pull rod (140) and / or for pulling the collet (120) out of the main body (110).

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