Patent Grant
7353676
This application claims priority to co-pending German Patent Application No. DE 10 2004 056 921.5 entitled “Verfahren und Vorrichtung zum Präzisionsrollen von rotations-symmetrischen Bauteilen”, filed Nov. 25, 2004.
The present invention generally relates to an apparatus for precision rolling of a surface area of a rotationally symmetrical component by at least two spaced apart rolling tools. The present invention also relates to a method for precision rolling of a surface area of a rotationally symmetrical component by at least two spaced apart rolling tools.
More particularly, the novel apparatus and method serve to produce profiled sections of a component or to finish profiled sections of a component, for example by calibrating. For example, the rotationally symmetrical component may be a worm wheel, an injection valve, a press fit shaft section, and the like. Preferably, the component is a fastener, especially a screw. For example, the profiled section may be a thread, a helix, a knurled portion, a grooved section, a helical profile or a toothed section. In addition to the production or finishing of profiled sections, it is also possible to produce or to finish non-profiled sections, especially by finish rolling of a smooth surface area of the component.
An apparatus and a method for precision rolling of a surface area of a rotationally symmetrical component by at least two spaced apart rolling tools and a unit for determining the actual blank diameter of the component are known from German Patent Application No. DE 31 10 433 A1 corresponding to British Patent Application No. GB 2 098 901 A The comparison of the actual blank diameter of the component and the desired blank diameter of the component is used as a decision criterion on passing or rejecting a component.
A profile rolling machine for deforming the surface area of rotationally symmetrical components is known from Swiss Patent No. CH 692 385 A5. The known profile rolling machine includes a machine base on which guiding rails for slides are mounted. The slides support rolling tools being designed as rolling heads, and they are movably supported along the guiding rails such that the distance between the rolling tools is adjustable by a relative movement of the slides with respect to one another along the guiding rails. The profile rolling machine further includes a load frame including two adjacent joke plates being arranged at the ends. The load frame is supported on the machine base to be movable in the direction of movement of the slides such that the machine base is decoupled from the load frame such that low rolling forces have to be accepted during deformation of a component. The known profile rolling machine includes a length measuring unit being located at the machine base. The position of the movable slide with respect to the machine base can be measured by the length measuring unit. Furthermore, there is a control unit which corrects the position of the rolling tools with respect to one another in response to possible length extensions of the load frame. Generally, the design of the known profile rolling machine is based on the concept of decoupling the machine base including the length measuring unit from the load frame including the rolling tools in a way that readjustment of the distance between the rolling tools in response to the distance measured between the rolling tools by the length measuring unit during rolling.
A method and an apparatus for finish rolling of smooth rotationally symmetrical components are known from East German Patent No. DD 288 787 A5. A numeric control machine tool includes a tool holder in which a rolling tool subjected to the force of a spring is located. A length measuring unit including electric contacts is connected to the shank of the rolling tool. The length measuring unit is connected to the control of the numeric control machine tool. The rolling force depending on the work piece and on the material of the work piece is adjusted in the desired tolerance range in the length measuring unit under consideration of the spring characteristic of the rolling tool. Deformation of the spring element in the rolling tool during rolling is used as an indirect measure of the occurring rolling force, and it is sensed by the length measuring unit. When the adjusted tolerance range is exceeded, pulses are initiated, the pulses being used to control the rolling force. Thus, it is desired to reach a rolling force which is as constant as possible no matter what the shape of the blank of the component is.
The present invention relates to an apparatus for precision rolling of a surface area of a rotationally symmetrical component. The apparatus includes at least two spaced apart rolling tools, a unit for determining an actual blank diameter of the component, a unit for comparing the determined actual blank diameter of the component with a predetermined blank diameter and for determining an adjustment value from the result of the comparison, and a control unit for adjusting a distance between the at least two rolling tools in response to the adjustment value.
The present invention also relates to an apparatus for rolling a surface area of a rotationally symmetrical component, especially a fastener. The apparatus includes at least two spaced apart rolling tools, a measuring unit, an evaluating unit and a control unit. The rolling tools are designed and arranged to machine at least a section of the surface area of the component by rolling. The rolling tools are designed and arranged such that a distance between the rolling tools is adjustable by moving the rolling tools with respect to one another. The measuring unit is designed and arranged to determine an actual blank diameter of the component. The blank diameter is a diameter of the component before rolling. The evaluating unit is designed and arranged to associate the determined actual blank diameter of the component to an adjustment value. The adjustment value is contained in a specific group of a plurality of groups. Each of the groups is associated with a plurality of predetermined blank diameters of the component. The control unit is designed and arranged to adjust the distance between the at least two rolling tools depending on the adjustment value.
The present invention also relates to a method of precision rolling of a surface area of a rotationally symmetrical component. The method includes the steps of determining an actual blank diameter of the component, comparing the determined actual blank diameter of the component with a predetermined blank diameter, determining an adjustment value from the result of the step of comparing, adjusting a distance between at least two rolling tools in response to the adjustment value, and machining at least a section of the surface area of the component by rolling.
The component to be processed by rolling is located between at least two spaced apart rolling tools, and it is machined in accordance with the shape of the rolling tools. During processing of the surface area of the component, there is the problem of the rolling tools being pressed away from one another due to the counterforce applied by the component. In prior art methods and apparatuses, this leads to the fact that the actual finished part diameter of the component substantially differs from the desired finished part diameter of the component in a way that the required process safety is not attained. This drawback is effectively overcome by the present invention.
The novel unit for determining the actual blank diameter of the component may be designed as a measuring unit. However, it may also be designed as an interface of the apparatus to be connected to a (separate) measuring unit. The unit for comparing the actual blank diameter of the component to the predetermined blank diameter and for determining an adjustment value from the result of the comparison of the actual blank diameter of the component to the predetermined blank diameter may be designed as an evaluating unit. However, it may also be designed as an interface of the apparatus to be connected to a (separate) evaluating unit. In other words, the apparatus does not need to include the measuring unit and/or the evaluating unit. The apparatus only needs to be designed such that data coming from a measuring unit can be transmitted to an evaluating unit and further to the control unit of the apparatus.
The novel method of precision rolling of a surface area of a rotationally symmetrical component on a rolling machine at first senses and determines the actual blank diameter of the component. Then, the actual blank diameter of the component is compared to a predetermined blank diameter, and an adjustment value is determined from the result of the comparison of the actual blank diameter of the component with the predetermined blank diameter. Next, the distance between the at least two rolling tools is adjusted in response to the adjustment value.
The present invention is based on the findings that the efforts known in the prior art to realize a distance between the rolling tools which is as constant as possible in the sense of an almost constant working end position of the rolling machine and great stiffness of the rolling machine do not lead to the required exactness of the finished part diameter of the component. The present invention intentionally leaves this prior art concept, and it replaces it by the concept of controlling the distance between the rolling tools in response to the result of the determination of the actual blank diameter of the component before being processed.
This novel concept of controlling the distance between the rolling tools in response to and depending on an adjustment value being based on the determined actual blank diameter of the component is based on the following findings: if a production lot of n components is to be rolled precisely and m components have an actual blank diameter in the range of the lower tolerance (meaning they are comparatively thin), one can observe that these m components also have a smaller diameter after precision rolling compared to the other “thicker” components. In other words, a “thin” component remains “thin” after precision rolling, and a “thick” component remains comparatively “thick” after precision rolling. The diameters of the components approximately have the same relation, the range in which the components are located being slightly decreased by precision rolling. For example, in a range of approximately 0.1 mm of the variation of the blank diameters, the decrease of the range is less than approximately 0.02 mm relating to the finished part diameters of the components. This leads to the conclusion that elastic deformation of the components during deformation increases during rolling.
The determined actual blank diameter of the component may be associated to a specific group of a plurality of groups, each of the groups containing a specific adjustment value. In this way, one attains the advantage of the control expenditure and the adjustment expenditure being minimized while still realizing sufficient exactness of the finished part diameter of the components. In this way, it is not necessary to move the rolling tools to a different position for each different component. The number of groups and the classification of groups or classes are realized depending on the tolerance of the blank diameters and the accepted finished part diameters of the components. Alternatively, the adjustment value can also be determined according to a mathematical function being specific for the machine or the material to be deformed.
The adjustment values may be determined based on a comparison of a determined actual finished part diameter of the component with a predetermined desired finished part diameter for each one of the plurality of groups. In other words, a characteristic curve of the respective rolling machine, the respective material and of the respective shape and geometry of the component is determined. For reasons of simplification, one may use the classification of the blank diameters.
For example, the measuring unit may be located in an automatic feeding unit for the components. It is possible to arrange the measuring unit and the actual apparatus for precision rolling (i.e. the rolling machine) at different places. The measuring unit does not necessarily have to be a direct part of the apparatus. One only needs to make sure that the measuring unit is associated with the evaluating unit in a way that the measuring data is electrically and electronically, respectively, transmitted such that the evaluating unit can determine the adjustment value based on the data, and such that it can transmit the adjustment value to the control unit for adjusting the distance between the at least two rolling tools. It is to be understood that the evaluating unit may also be designed and arranged to be separate from the apparatus.
For example, the measuring unit may be designed as a mechanical measuring unit or as an optical measuring unit. When using a mechanical measuring unit, the diameter of the component may be determined by a mechanical tracer, for example. When using an optical measuring unit, it may include light barriers or cameras, for example. The component to be deformed by rolling may especially be a fastener, preferably a screw. For screws, especially rolling of profiled sections is a common case of application. The shank of a screw is cold formed by rolling, for example to produce a thread, a helix being located in a fitting portion or a knurled element.
Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and the detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention, as defined by the claims.
The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. In the drawings, like reference numerals designate corresponding parts throughout the several views.
Referring now in greater detail to the drawings,
If one applies these findings to the process of precision rolling (see
The novel control principle of the apparatus 1 and of the method of precision rolling of the surface area 2 of a rotationally symmetrical component 3 conducted by the apparatus 1 are explained in greater detail in the following with respect to
However, it is also possible to design and arrange the apparatus 1 to be separate from the measuring unit 9 and/or from the evaluating unit 10. In such a case, the apparatus 1 and its control unit 11, respectively, has a respective interface. The measuring unit 9 does not have to be designed as a direct component of the apparatus 1. The measuring unit 9 is associated with the evaluating unit 10 such that the units 9, 10 are connected to transmit the sensed data electrically and electronically, respectively. In this way, the evaluating unit 10 determines the adjustment value based on the sensed data, and it transmits the adjustment value to the control unit 11 for adjustment of the distance between the at least two rolling tools 4, 5.
A first exemplary embodiment of the novel apparatus 1 is illustrated in greater detail in
Another exemplary embodiment of the novel apparatus 1 is illustrated in
Preferably, in an initiating step, one first determines a characteristic curve relating to the specific kind of component 3 to be processed in the specific apparatus 1 by conducting the deforming method without varying the distance between the rolling tools 4, 5. For this purpose, the blank diameters of components 3 of different blank diameters are processed in the apparatus 1 by rolling, and the resulting finished part diameters are sensed and determined by a measuring unit. The adjustment values are then determined based on the difference between the desired diameter of the finished part and the actual diameter of the finished part. It has been found to be advantageous to choose a plurality of diameter classes or groups, to classify the diameters according to the diameter classes, and to associate different adjustment values with each one of the diameter classes. Depending on the permissible variation or tolerance of the diameter of the finished part compared to the permissible variation or tolerance of the blank diameters, the blank diameters are classified in more or fewer classes. For example, in case the variations of the blank diameters are great and/or the accepted tolerances of the diameter of the finished parts are small, one chooses a comparatively great number of classes. These classes are then used for the mass production of a specific kind of a component 3 to be processed in the specific apparatus 1.
Preferably, the outer diameter of a finished part is sensed and determined as the diameter of the finished part. Depending on the requirements to the component 3, it is also possible to use a different location of the component 3 for measuring purposes, for example the flank diameter or the core diameter of a thread or of a profiled section of the component 3.
Due to the desired control of the distance between the at least two rolling tools 4, 5 in response to an adjustment value being derived from the blank diameter of the component, it is possible to accept greater tolerances and variations of the blank diameter of the component since elasticity of the apparatus 1 (which can never be reduced to zero) is almost completely compensated by the control operation. Furthermore, it is possible to design the apparatus 1 to have a more simple structure, for example by not using elements for stiffening purposes and decoupling purposes. Thus, the production costs of the apparatus 1 can be reduced compared to prior art apparatuses.
The advantages which may be realized by the novel apparatus 1 compared to prior art apparatuses may be especially seen from the diagram according to
In this way, with the present invention, it is now possible to attain great exactness of the diameter of the finished part of the component 3 even when there are great variations of the blank diameters of the component 3 without having to take special measures with respect to the stiffness of the apparatus 1. Thus, the requirements of process safety are fulfilled. For example, when using an outer diameter of the component 3 of approximately 22 mm, an exactness of ±10 μm of the finished part diameter of the component 3 can be attained. When using an outer diameter of the component 3 of approximately 8.5 mm, for example, an exactness of ±5 μm of the finished part diameter of the component 3 can be securely realized.
Many variations and modifications may be made to the preferred embodiments of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of the present invention, as defined by the following claims.
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| 10 2004 056 921 | Nov 2004 | DE | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20060107717 A1 | May 2006 | US |
