Patent Application
20140113535
The invention relates to a honing tool for machining cylindrical bores, wherein the honing tool has a tool body and in the tool body a guide bore for a feed rod is formed. The honing tool further comprises at least one honing stone receptacle that is extending from the guide bore radially in outward direction through the tool body and is designed for receiving at least one honing stone.
In honing tools known in the art, the dimensions of the usually rectangular honing stone receptacle and of the corresponding honing stones are matched to each other such that the honing stone is received and guided between the boundary surfaces of the honing stone receptacle so as to be radially movable and arranged without play in the circumferential direction of the tool body. Generally, by precise machining of the boundary surfaces of the honing stone receptacle and of the corresponding lateral surfaces of the honing stone, it is attempted to realize a sliding fit so that the honing stone can be barely inserted by hand into the honing stone receptacle and is secured in the honing stone receptacle by friction between the lateral surface of the honing stone and the adjoining boundary surface of the honing stone receptacle.
The inner side of the honing stone that is projecting into the interior of the tool body has generally a slanted or inclined bottom side which is interacting with a corresponding wedge surface at the end of a feed rod in such a way that an axial displacement of the feed rod relative to the tool body causes a radial displacement (advancing or feeding action) of the honing stone in outward direction. Examples of such honing tools are disclosed in WO 01/39926 A1 and US 2011/0223843 A1.
Particularly when machining bores with relatively small diameters, for example, in a diameter range of 15 mm or less, honing tools are used which have a tubular tool body that is attached with a first end section in a tool shaft and is provided at the opposite second end section with a cutting area with at least one honing stone receptacle that extends all the way through the tool body from the interior of the tool body in outward direction and is designed for receiving a honing stone. The tool body serves in this context as a receptacle for one or several honing stones and, at the same time, as a guide for a feed rod that serves for radial feeding of the honing stones. The tool shaft serves, on the one hand, for receiving the tool body and, on the other hand, for attachment of the honing tool on the work spindle of a honing machine.
In honing tools for machining bores with small diameters (i.e., smaller than 15 mm), there is of course little space available in the tool body. Also, the tool body should be weakened as little as possible so that it maintains its torsional stiffness resulting from its tubular configuration.
On the other hand, it must be ensured that the honing stones will not be thrown out of the honing tool by the centrifugal forces that are acting in operation of the honing tool and that the honing stones, after completion of a machining operation, are automatically returned into the tool body so that upon insertion of the honing tool into the next bore to be machined no collision between the top edge of the bore and the bottom edge of the honing stone will occur.
US 2011/0223843 A1 discloses securing of a honing stone relative to centrifugal forces by means of an elastic deformable support element which is acting between a lateral surface of the honing stone and the oppositely positioned boundary surface of a honing stone receptacle. The support element is recessed in a lateral surface of the honing stone below a cutting layer of the honing stone within a rounded groove extending parallel to the longitudinal axis of the honing stone. The support element acts as play compensation device that compensates play between the contact surfaces. The support element prevents also that the honing stone will be thrown off when the honing tool is rotating.
As an alternative solution it is known that, at a right angle to the longitudinal direction of the honing stone, bores are introduced into the base of the honing stone into which an elastic element is then inserted, for example, a section of an O-ring that has a projecting portion relative to the thickness of the honing stone and that, when inserted into the honing stone receptacle, also acts to compensate play and compensate wear. This embodiment increases also the costs of the honing stone.
It is the object of the present invention to provide a tool with improved cost efficiency that operates reliably even after extended operational use and in which the honing stone is reliably held in the honing stone receptacle. In particular, radial mobility of the honing stone in the honing stone receptacle and, simultaneously, a satisfactory safety relative to centrifugal force action should be ensured permanently. These objects are to be realized as simply and as inexpensively as possible.
In accordance with the present invention, this is achieved in that the honing tool of the aforementioned kind has an elongate spring element arranged in the tool body parallel to the at least one honing stone. A central section of the spring element is guided across a pin which is laterally projecting from the honing stone. At least one of the end sections of the spring element is secured in radial direction in the tool body.
With the spring element according to the invention which is integrated completely into the tool body of the honing tool, it is possible to exert a spring force in radial direction onto the honing stone which forces the honing stone in radial direction inwardly into the tool body. In this way, it is ensured that, firstly, the honing stone always remains in contact with a wedge surface of the feed rod and that, secondly, upon retraction of the feed rod the honing stone is returned into its rest position by the spring force of the spring element, i.e., is forced in radial direction inwardly into the tool body. The spring element according to the invention is very small with respect to its dimensions, in particular, when it is made of spring wire (diameter e.g. 0.3 mm-1.0 mm). As a result of this, the tool body of the honing tool must be weakened only minimally in order to accommodate and radially secure the spring element. In this context, sufficiently large spring travel and, simultaneously, satisfactory spring or restoring forces can be provided by appropriately selecting the length of the spring element and the pretension of the spring element.
In order for the pin, which is projecting laterally from at least one face of the honing stone, and the central section of the spring element, which is entrained by the pin, to be freely movable within the tool body, according to a configuration of the honing tool in accordance the invention it is provided that laterally at one side or both sides of the honing stone receptacle a pocket is formed in the tool body. Since the spring element requires only little space and therefore also the pin can be short, this pocket can be designed relatively flat so that even with this pocket no significant weakening of the tool body occurs. In particular, the guiding action of the honing stone within the honing stone receptacle is not significantly worsened because this pocket is generally provided approximately at the center of the honing stone receptacle.
A particularly simple configuration for securing the spring element radially within the tool body is a groove provided either at one end of the pocket or at both ends of the pocket, wherein one or both end sections of the spring element are inserted into the single groove or both grooves. In this way, the spring element is secured in radial direction in the tool body. With regard to manufacture, these grooves can be realized in a simple way and do not require great precision due to the spring properties of the spring element.
It has been found to be advantageous in many embodiments when the groove, be it a groove adjoining one end of the pocket or a groove that essentially bridges the pocket, is shorter than the honing stone receptacle. In this case, the guiding action of the honing stone in the honing stone receptacle is still ensured and weakening of the tool body is relatively minimal. This is particularly true because the relevant forces are transmitted between honing stone and tool body at the ends of the honing stone receptacle. These areas are neither weakened by the pocket nor by the groove so that the torsional stiffness of the tool body is substantially unchanged. In a preferred embodiment of the invention, the groove extends substantially parallel to a longitudinal axis or a wedge surface of the feed rod.
It is also possible that, viewed in axial direction, in front of or downstream of the pocket there is a short groove or even only a transverse bore in order to secure the spring element in radial direction. When two short grooves are formed at both ends of the pocket, these grooves can be arranged at a spacing to the pocket so that in this way a further increase of the stiffness of the tool body results.
In this embodiment it is advantageous when the spring element is angled at one end section or both end sections so that with the angled end it can be inserted into the short groove or into the transverse bore which is provided in the tool body.
In many embodiments, it can be advantageous and/or necessary to close the groove again after the spring element has been inserted into the groove. This can be done e.g. by a (round) cord of an elastomer, a securing pin or a similar device. In this way, it is ensured that the spring element cannot jump out of the groove. On the other hand, it is easy to access the spring element again; this significantly facilitates the exchange of a worn honing stone.
When only at one side of the honing stone receptacle a pocket is formed, it is advantageous when this pocket is arranged on the side which is leading in the rotational direction of the honing tool. In this case, the honing tool during machining is supported on the side that is not weakened by a pocket; this positively affects the precision of the guiding action of the honing stone and the service life of the honing tool.
In many embodiments, it is however advantageous when at both faces of the honing stone a spring element, a pocket, and at least one groove are arranged. In this case, the pin projects at both faces of the honing stone laterally from the honing stone and the restoring forces are uniformly applied onto the honing stone so that tilting or canting of the honing stone in the honing stone receptacle is effectively prevented. Moreover, this provides redundancy so that, when one spring element fails, full functionality of the honing tool according to the invention is still provided.
It can be advantageous to connect the two spring elements by means of a bracket with each other. With this bracket, the number of components that must be mounted independently is reduced so that exchange of a honing stone is significantly simplified. This is particularly true when the spring element and the bracket are made of a single piece (monolithic), in particular, a single piece of spring wire.
In this embodiment, the feed rod is advantageously provided with a cutout for the bracket. In this way, the spring elements are secured on the feed rod. They cannot slide laterally because this is prevented by the bracket and the spring elements forming together a U-shaped structure. Also, the spring elements follow the feed movements of the feed rod. In this way, it is possible to realize a linear, degressive or progressive course of the spring force as a function of the position of the feed rod.
As already mentioned, it may be advantageous that at least one end section or both end sections of the spring element are angled wherein the angled end or ends of the spring element engage a groove provided in the tool body or in the honing stone.
The aforementioned object is also solved by a honing tool of the aforementioned kind in that in the honing stone at least one longitudinal groove is provided, in that the at least one longitudinal groove extends parallel to a bottom side of the honing stone, in that in the feed rod a circumferential groove is formed, in that in the circumferential groove a U-shaped securing element is arranged, and in that one end of the securing element engages the at least one longitudinal groove of the honing stone.
In this embodiment, the honing stone is secured with positive fit (form fit) at the wedge surface of the feed rod so that upon retraction of the feed rod the honing stone is retracted automatically in radial direction because of the positive locking action with the feed rod and moved inwardly into the tool body. This embodiment is simple with respect to manufacture and enables a rigid coupling between feed rod and honing stone.
It is also possible that two such securing elements are arranged in axial direction of the feed rod at a spacing relative to each other so that the honing stone at its leading end as well as at its trailing end is coupled positively with the feed rod.
In this case, it is then also possible to provide one longitudinal groove each on the faces of the honing stone, respectively, so that the risk of tilting or canting is also prevented. Of course, it is also possible to provide a securing element whose two ends are angled so that they each engage a longitudinal groove provided at both faces of the honing stone, respectively.
In order to improve mounting and exchange of a honing stone in this embodiment, it is provided that in the tool body a mounting opening and/or a detachable closure cap is formed. The closure cap would provide the advantage that it would enhance the torsion stiffness of the tool body in operation and would be easily detachable simply by unscrewing and attachable again by screwing it.
The securing elements or the spring elements are preferably manufactured of wire, in particular spring wire. Therefore, they are inexpensive with respect to manufacture, are very load-resistant, and require only little space for installation.
These and further features are disclosed, aside from the disclosure in the claims, also in the description and the drawings. Individual features considered individually or several combined in the form of sub-combinations can be advantageously realized in an embodiment of the invention as well as in other fields and may constitute advantageous further inventive embodiments or variants. Embodiments of the invention are illustrated in the Figures and will be explained in more detail in the following.
The honing tool 100 illustrated in
In order to effect radial feeding of the honing stone 104, in the interior of the tool body 102 a feed bore 108 is formed (see
The honing stone 104 is guided in a honing stone receptacle 114 of the tool body 102 axially and laterally as much as possible without play so that the single degree of freedom of the honing stone 104 is a radial feed movement.
The honing stone receptacle 114 extends radially from the guide bore 108 to the outer diameter of the tool body 102.
For simplifying matters, in connection with the invention the term honing stone 104 is always used. It is to be understood that the radial inwardly arranged part of the honing stone 104 is comprised of metal and, onto the radial outwardly arranged part of the honing stone 104, the actual cutting layer is sintered or attached in another way. Of course, constructions are also possible that have a separate support bar onto which the actual honing stone is mounted. Both variants are referred to in connection with the invention as honing stone.
When looking at
As can be seen in particular in
The end sections 122 are received in a groove 124 in the tool body 102 in such a way that they are fixed in radial direction. In axial direction, a certain play is existing between the ends 122 of the spring element 118 and the groove 124. The groove 124 extends parallel to the longitudinal axis of the tool body 102. The spring element 118 can already be somewhat pre-bent or can be made as a straight piece of spring wire that is subjected to deformation upon mounting as it is lifted across the pin 116.
In this way, the spring element 118, whose end sections 122 are received in the groove 124, effects a radial inwardly oriented spring force onto the pin 116 and thus onto the honing stone 104.
When the feed rod 110 is now retracted, i.e., in
In order to provide space for the pin 116 and the central section 120 of the spring element 118, a pocket 126 is cut into the longitudinal side of the honing stone receptacle 114.
This pocket 126 is illustrated primarily in
In order to prevent the spring element 118 from falling out of the groove 124, a rubber cord 128 can be pressed into the groove 124. The captive action in the form of a rubber cord 128 can also be achieved by a securing screw or by another equivalent device.
In
In the feed rod 110 there is therefore a recess 132 so that the bracket 130 connecting the spring elements 118 can be inserted and received in this recess 132 and does not project past the feed rod. This means that the spring elements 118 will be entrained by the movement of the feed rod 110 and therefore are moved relative to the tool body 102 and to the pin 116. In
The two spring elements 118, as is shown in
Since in this embodiment two spring elements 118 effect the restoring action of the honing stone 104 and these two spring elements engage on both faces of the honing stone 104, higher restoring forces can be achieved, of course. Also, tilting or canting of the honing stone 104 in the honing stone receptacle 114 is reliably prevented.
In
In this embodiment, the elongate spring element 118 is angled at both end sections 122 and is inserted with these two angled end sections 122 into a groove 124 in the tool body 102. This is particularly well illustrated in
Because in this embodiment the spring element 118 is radially secured in the tool body 102 and not entrained by the feed rod 110, it is possible to form the central section 120 of the spring element 118 as “half” an eye 134. This eye 134 engages about the pin 116 of the honing stone 104. As can be seen in
In order to weaken the tool body 102 as little as possible, the pocket 126 is essentially of a stepped configuration. This means that at the face where the pin 116 is located the pocket 126 is somewhat deeper in order to be able to slide the spring element 118 upon demounting the honing tool laterally from the pin. In
In
In this embodiment, the spring element 118 is essentially clamped with one end section in the groove 124. The other angled end section 138 passes through a cutout 140 into a transverse bore 142 of the honing stone 104 and secures the honing stone 104 in contact at the feed rod (not illustrated in
In this way, the torsional stiffness of the tool body 102 is further improved. In
In this embodiment, parallel to the wedge surface 112 and thus also parallel to the bottom edge of the honing stone 104, a groove 148 is cut into the honing stone 104. A circumferential groove 150 that serves for receiving a securing element 152 is machined into the feed rod 110. An angled end 154 of the securing element 152 engages the groove 148 and therefore provides a positive fit connection between the honing stone 104 and the feed rod 110. The securing element 152, as already mentioned, is arranged in the circumferential groove 150 of the feed rod 110 so that it follows the movements of the feed rod 110. The angled end 154 of the securing element 152 moves then through the groove 148 in the honing stone 104 so that no distortion results and, on the other hand, the bottom side 156 of the honing stone 104 is in contact with the wedge surface 112 of the feed rod 110.
It is, of course, also possible to provide on both faces of the honing stone 104 a groove 148 and to secure the honing stone 104 by means of two securing elements 152 which are received in two spaced-apart circumferential grooves 150 of the feed rod 110. It is also possible that two spaced-apart securing elements 152 with their angled ends 154 engage the same groove 148 of the honing stone 104.
Preferred embodiments of the honing tool 100 according to the invention are provided for machining relatively small bores and have, for example, an effective diameter of 15 mm or less, in particular 10 mm or less. Typically, the effective diameter can be between approximately 5 mm and approximately 10 mm. Of course, it is also possible to use the described embodiments in honing tools with greater diameters.
The specification incorporates by reference the entire disclosure of German priority document 20 2012 010 023.8 having a filing date of Oct. 19, 2012.
While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202012010023.8 | Oct 2012 | DE | national |
