Abstract:
A method for lengthening the machining travel of a machine-tool operating at a very high speed, including a tool-carrying ram mobile on three axes. The method combines with the machining movements of the tool-carrying ram along one or several axes, one or several rectilinear movements of the part to be machined by parametering and digitizing the relative travels and speeds of the part to be machined with respect to the tool-carrying ram. The invention also concerns the device for implementing this method and the machine-tool using such a device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of high speed machining, machine-tools mobile on three axes X, Y and Z, and more particularly to modifications allowing to improve the machining travel of this type of machine. 
     2. Discussion of the Background 
     Classically, the tools used in very high speed machining are of the rotary type and are placed at the end of a unique tool-carrying ram mounted moveable along three axes so as to allow machining on a big length, a big width and a big depth, as well as tool exchange, gripping and collection functions in magazines conceived for that purpose. 
     Generally, these machines comprise several main parts, i.e.: 
     an actual machining station comprising the tool driven in rotation at the end of the ram and shaping the part to be machined, 
     a driving station placed near the machining station and constituted by a combination of driving mechanisms ensuring the movements along the axes X, Y, Z of the tool-carrying ram, which also ensures, via an electric spindle, the rotary movement of the tool carried at the end, 
     a control station collaborating with the driving station according to a pre-established instructions program to ensure and to manage the different machining operations and stages of the different parts to be machined. 
     The machining station can classically comprise several subsets offering as many additional functions. Thus, for example, a magazine or a tool storage device offers several machining tools to the ram mobile on three axes coming to leave and take the tools, allowing it to ensure as many machining functions as possible on a part to be machined. The machining station can also comprise a device for exchanging parts to be machined managed by the control module and ensuring the exchange between the parts having just been machined and the ones still to be machined. 
     With the benefit of its experience in the field of high speed machining along three axes and on machines called mono-spindle, the applicant has conceived high precision machines operating at a high velocity capable of achieving high accelerations and rapidity of function in their movement along three axes X, Y and Z by the use of a logical cinematic structure and innovative driving means, well above that achievable by classical machining machines. The applicant has noticed that these machines, even though they have matched the users requirements up until now, can in some situations prove to have limited use in their machining travel. In fact, to reply to the new criteria of acceleration and rapidity of function required for very high speed machining machine-tools, combined with the concern for compactness of the machines, the travels along the three different axes are comprised in intervals defined by the mechanical or geometrical limits of the machine, which intervals can prove to be too short for some applications. 
     The limitation to the travel is a difficulty often found in the conception of machine-tools and several devices can be found in the prior art, ensuring a movement of the part to be machined so as to enable it to get nearer the tool thus avoiding unnecessary travel and travel times (until the tool is in contact with the part to be machined and begins the machining stage) which would reduce the machine&#39;s performance. Nevertheless, no device has been conceived to enable the lengthening of the machining travel of a machining machine-tool of the type comprising a tool-carrying ram which, ensuring functions of tool gripping, exchange, guidance, and driving moves along three axes X, Y and Z, the three axes forming an orthogonal spatial system of axes and Z being the longitudinal axis of the machine and of which the movements are ensured by linear motors, such as in the case of the machines conceived by the applicant. In fact, the total freedom of movement of the tool-carrying ram combined with its speed due to the use of linear motors, brings new technical criteria and opens a field of possibilities in programming machining on one part to be machined, never previously reached. The existing machine-tools using a tool-carrying ram moving along three axes are, on the whole, less fast and and less precise, and do not have the dynamic constraints of the ones conceived by the applicant, in view of their size, higher travels obtained, or less performing driving means. In addition, the existing devices which ensure the movement of a part to be machined are essential to the following machining stage because the tools of the classical machine-tools do not move parallel to the movements of the part to be machined. Thus, on the axes followed for the movements of the part to be machined, the ram, the headstock and/or the tool-carrying spindle stay fixed. 
     The applicant has thus studied the concept of an innovative method enabling the widening of the capacities of machines&#39; machining travel. The difficulty of such a concept is to offer a device enabling to adapt to a machine already answering perfectly to users&#39; requirements in most applications and for most of the parts to be machined so that it is not built-into the machine to avoid an overload when the device is not necessary. Furthermore, as the increase of the lengths of machining travels of a machine-tool have for direct and known consequence to reduce the velocity of the machine, such a device would be set in motion or would start to function only when the part or the side of the part to be machined (via a machining program) so requires. 
     SUMMARY OF THE INVENTION 
     In view of this situation and the specifications required, the applicant has carried out research aimed at achieving the aforementioned targets. This research has led to the conception of a method which does not reduce the performance of the basic machining machine-tool, integrable but not built-in to it, and enabling once it has started to function, the machining of parts to be machined which are longer, wider or higher. 
     According to the main characteristic of the invention, the method for lenghtening the machining travel of a high speed machine-tool of the type comprising a tool-carrying ram ensuring tool gripping, exchange, guidance and driving and moving along three axes X, Y and Z, the three axes forming an orthogonal spatial system of axes and Z being the longitudinal axis of the machine, the movements being ensured by linear motors, is remarkable in that it consists in combining to the machining movements of the tool-carrying ram along one or several axes, one or several rectilinear movements of the part to be machined by parametering and digitizing the relative travels and speeds of the part to be machined with respect to the tool-carrying ram. 
     This method is particularly advantageous as it enables to lengthen the useful travel of the tool-carrying ram of the machine-tool without reducing the dynamic performances. In fact, the mobility on one or several axes of the part to be machined with respect to the tool-carrying ram already mobile on these three axes enables not only to bring the part to be machined closer to avoid the non machining times and reduce the unecessary travel of the tool-carrying ram, which is what classically occurred in the devices of the prior art but also to reduce these times of bringing closer by moving the tool-carrying ram and the part to be machined along parallel axes but in an opposite way thus reducing dead time. 
     In this precise application, once the part to be machined and the tool-carrying ram are close, several machining configurations are possible: 
     either the tool-carrying ram is alone in executing the travel and rotatably driving the tool towards the fixed part to be machined, 
     or the part to be machined is alone in executing the travel in moving towards the tool-carrying ram fixed with the tool rotatably driven, 
     or the part to be machined and the tool-carrying ram both move along a parallel direction but in an opposite way. 
     According to a particularly advantageous characteristic of the invention, this method consists in parametering and digitizing the relative travels and speeds of the part to be machined with respect to the travels on axis Z of the tool-carrying ram. This characteristic is particularly innovative in view of the fact that most machine-tools do not use a tool-carrying ram ensuring a translation on axis Z and they consequently do not ensure the suitability between the translation on axis Z of the tool-carrying ram and a translation parallel with axis Z of the part to be machined in a same direction. This suitability thus requires the mastering of new parameters. 
     The invention also concerns the device enabling to implement the method for lengthening the machining travel of a high speed machine-tool of the type comprising a tool-carrying ram moving along three axes X, Y and Z, the three axes forming an orthogonal spatial system of axes and Z being the longitudinal axis of the machine, the movements being ensured by linear motors. This device is remarkable in that it comprises inside the machining zone, a part-carrying clamping subset combined with a driving subset ensuring the translation on one or several axes parallel with the axes of the movements of the tool-carring ram, of the part-carrying clamping subset. Furthermore, the driving subset comprises linear motors which drive in translation, synchronising with the movements of the tool-carrying ram on a pair of rails respectively parallel with axes X, Y and Z of the movement of the tool-carrying ram, the part-carrying clamping subset. This consistency in the choice of driving means enables to produce movements of the parts to be machined as fast as the movements of the tool-carrying ram and avoids to penalize the performance of the whole of the machine while ensuring a lengthening of the travels. 
     Also, contrary to the devices of the prior art, the movement of the part to be machined is not necessary to the functioning of the machine-tool during simple machining thus enabling to leave the part to be machined in fixed position. 
     The invention also concerns a machining machine-tool adopting the device of the invention. This machine-tool is of the type comprising a machining station, a driving station, a control station, the machining station taking up at least one mobile set for moving or exchanging the parts to be machined of the invention, the mobile set comprising a sealed device isolating the machining station from the outside so as to avoid projections of swarf and is remarkable in that it develops itself around the mobile subset, and thus from its own leaktightness device, an isolating device, linked to its frame, separating the machining station and the elements it is made of from the outside. 
     This characteristic justifies itself by the new constraints required for the speed of movement during the movements of the parts to be machined. In fact, such devices for exchanging parts or for moving parts to be machined, classically comprises a leaktightness device constituted by a cover and a separating wall which enables to isolate the machining station and to avoid the projection of swarf inside. The movements of the device of the invention have forced the designers to ensure leaktightness of the mobile set with respect to the fixed frame of the machine by rubbing. Therefore, the criteria of speed required for the movements of such a device are such that the rubbing must be limited as far as possible to the detriment of the leaktightness against swarf. Thus, the technological solution of the invention enables to create a second protection around the elements constituting the machining station of the machine-tool so as to avoid the spreading of swarf which would have gone through the first cover or through the first protection. Another advantage of this double protection is that, even though they are protected by their own cover or separating wall, the elements constituting the machining station of the machine-tool and more particularly the lengthening device of the travel of the invention which is a mobile device can work out to be dangerous for any nearby handlers, users or technicians. The presence of this second protection thus enables to answer to the safety at work criteria. 
     The fundamental concepts of the invention having just been detailed hereinabove in their most elementary form, more details and characteristics will come out more clearly when reading the description hereinafter using as a non limitative and having regard to the attached drawings, a device enabling to implement the method of the invention and of a machine-tool using such a device in accordance with the invention. 
    
    
     This description refers to the enclosed drawings on which: 
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     FIG. 1 is a perspective view of a machine-tool comprising a device in accordance with the invention, 
     FIG. 2 is a perspective view of the lengthening device of the machining travel in accordance with the invention, 
     FIG. 3 is a perspective view of a machine-tool in accordance with the invention comprising an added leaktight wall. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As illustrated on the drawing of FIG. 1, the device for lengthening the machining travel referenced as  100  as a whole is placed against a machining machine-tool M operating at high speed of the type comprising a tool-carrying ram  200  moving along three axes X, Y and Z the three axes forming an orthogonal spatial system of axes and Z being the longitudinal axis of the machine, the movements being ensured by linear motors. This machining machine-tool classically comprises several main parts, i.e.: 
     an actual machining station P 1  comprising the tool rotatably driven at the end of the tool-carrying ram  200  and shaping the part to be machined, 
     a driving station P 2  situated after the machining station P 1  and constituted by a set of driving mechanisms ensuring the movements along the axes X, Y and Z of the tool-carrying ram  200 , which also ensures, via an electric spindle, the rotary movement of the tool carried at the end, 
     a control station P 3  collaborating with the driving station P 2  according to a pre-established instructions program to ensure and to manage the different machining operations and stages of the different parts to be machined. 
     The machine-tool M such as illustrated also comprises a tool storage device  300  which offers several machining tools to the tool-carrying ram  200  coming to take and leave them enabling the tool-carrying ram  200  to ensure as many machining functions as possible on a part to be machined. 
     As illustrated on the drawing of FIG.  2  and according to a particularly advantageous characteristic of the invention, the lengthening device  100  is made of, inside the machining station P 1 , a part-carrying clamping subset  110  combined with a driving subset  120  ensuring the translation parallel with axis Z of the movement of the tool-carrying ram, of the part-carrying clamping subset  110 . 
     This sole additional translation combined with the movements along three axes of the tool-carrying ram  200 , enables to answer to the lengthening needs of the machining travels along the three classical axes. In fact, according to a non limitative embodiment, the part-carrying clamping subset  110  comprises a rotation axis, classically called axis B so as to present, to the tool-carrying ram  200 , the different sides of the part to be machined. This rotation movement combined with the Z translation movement of the part to be machined and the possibilities of tool movements and tool exchange of the tool-carrying ram  200  enables to achieve, while lengthening the travel, most machining stages. 
     Furthermore, the mobility of the part-carrying clamping subset  110  has for other advantage that it enables its classical rotation along a vertical axis (usually called axis B) parallel with axis Y. The speed of execution of a machining stage requires the maximum closeness between the part to be machined and the tool-carrying ram  200 , such closeness even though possible, would prevent the rotation of the part when the machining stage changes by direct contact of the part on the tool or on the tool-carrying ram. 
     Furthermore, on other configurations, the part-carrying clamping subset  110  ensures the support of several parts to be machined separated by a leaktighness wall preventing the projection of machining swarf on the parts not yet machined or on the system of axes of this one when they are removed from the part-carrying clamping subset. Such leaktightness walls are integral with the part-carrying clamping subset  110  and rotate at the same time which implies that the machining station must be wide enough to enable such a rotation. The translation of the part-carrying clamping subset thus enables the rotation of parts and of voluminous machining sets which would be impossible to use in a device of fixed classical part-carrying clamping subset which eases greatly the setting of the machining assembly and of the machining station cubicle. 
     As illustrated on the drawing of FIG.  2  and according to a particularly advantageous characteristic of the invention, the driving subset  120  comprises linear motors which drive in translation, in synchronisation with the movements of the tool-carrying ram  200 , on a pair of rails  121  and  122  parallel with axis Z of the movement of the tool-carrying ram  200 , the part-carrying clamping subset  110 . The advantage of using a pair of rails is that it enables the use of linear motors in good conditions. Furthermore, the combination of linear motors with rails is the same driving technology as the one used for the movements of the tool-carrying ram, which not only enables to ease the piloting to drive the part to be machined in synchronisation with those of the tool-carrying ram  200  but also to offer dynamic acceleration and speed characteristics of the movements of the part equivalent to those of the movements of the tool-carrying ram  200 . 
     According to a preferred embodiment of the invention, the rails  121  and  122  of the travel lengthening device  100  and their driving means, in this context of the linear motors, are protected against the projection of swarf by a telescopic cowling  130  (represented in broken line). In addition, still in the context of a discharge or protection of the part-carrying clamping subset  110  against swarf, the telescopic cowling  130  comprises along the travel and on each side, a discharge device  140  and  150  of the swarf, of the Archimede screw type bringing back the swarf towards the orifice  160  of main discharge of the machining station. 
     According to a particularly judicious characteristic of the invention, the part-carrying clamping subset  110  allows access, when it moves away from the vertical plane of machining of the machine-tool M, to housings which ensure the storage of tools of a large dimension arranged so that the tool-carrying ram  200  can ensure their gripping. Thus, the tools which cannot be stored in the storing device  300  because of their length can be arranged in housings which are not accessible during a simple machining stage because of the closeness of the part but when this or these tools are needed in machining, these housings become not only accessible but also useable by the tool-carrying ram  200  by the reversing of the part-carrying clamping subset  110 . 
     According to a particularly advantageous characteristic of the invention, the device  100  of the invention comprises housings enabling to receive large dimension tools accessible to the tool-carrying ram so that the latter can ensure their gripping. In this configuration, the device  100  enabling to move the part to be machined, ensures the function of a tool magazine coming to place in the action range of the tool-carrying ram  200  tools of large dimension needed for the machining of the part governed on the device  100 . 
     As illustrated on the drawing of FIG. 3, the machining machine-tool referencd as M as a whole is of the type comprising a machining station P 1 , a driving station P 2 , a control station P 3  and of which the machininig station P 1  comprises a device  100  for lengthening the machining travel of parts to be machined in accordance with the invention. As described hereinabove, such mobile devices  100  classically comprise a leaktightness device isolating the immediate machining zone around the tool-carrying ram  200  and that part to be machined to prevent the projection of swarf. 
     According to a particularly judicious technological choice, this machine M comprises, around the mobile set and its leaktightness device, an additional leaktightness wall  400 , linked to the frame, surrounding the machining station as a whole by separating it from the outside. The aim of this leaktightness wall  400  is to improve leaktightness of the machining station in relation to the outside environment and this for two main reasons: 
     one is that the leaktightness of the machining station is difficult to guaranty when the part-carrying clamping subset such as the invention is mobile, 
     the other is that handling, or technical interventions can be particularly dangerous if they are carried out in the vicinity of a mobile subset. 
     According to an advantageous but non limitative embodiment, the leaktightness wall  400  is constituted by an outer cover which extends the frame of the machine-tool from its machining station and takes up about the same outside dimensions at the level of the width and the height. 
     This technological choice has another particularly advantageous consequence: the storage devices and more particularly the rotary storage devices such as illustrated on the drawing of FIG.  3  and referenced as  300  and  300 ′ are classically arranged inside a sealed chamber of dimensions enabling their rotation and enabling the tool-carrying ram to have the stored tools at its disposal. They can move in the space separating the first wall isolating the immediate environment of the machining zone (i.e. the tool, the tool-carrying ram and the part to be machined), the machining zone being defined by the leaktightness device of the part-carrying device and by the wall of the machine-tool machining station, of the second wall  400  thus avoiding the use of a specific sealed chamber to the tool magazine. 
     The use of dimensions about equal to the dimensions of the outer frame of the machine-tool M in width and in height has for advantage to respect the compactness criteria required for the dimensions of such machines. 
     As illustrated and according to a particularly advantageous characteristic of the invention, the outer cover  400  is parallelepipedic and comprises three openings  410 ,  420 ,  430  allowing access to the inside and/or to the elements constituting the machining station. Thus, the openings  410  and  420  are, according to a preferred embodiment of the invention, sliding doors enabling according to the sliding travel to allow access progressively: 
     to the tool housings of the rotary tool magazines  300  and  300 ′ when those are stopped but during machining in view of the presence of the first leaktightness wall, 
     to the mobile device in accordance with the invention. 
     These different openings are advantageously fitted with inspection windows enabling to control the good working order of the machine-tool. 
     In this precise case, the principle of double cover has for other advantage to reduce the shock-proof protection surface which must surround according to safety rules the machining station and thus reduce the material costs. This second outer cover indeed enables that only the immediate machining zone around the tool and the part to be machined are protected by armoured windows, and steel walls. The rest of the machining station can be protected or isolated from outside by the second wall  400  which can be advantageously made from less resistant and thus cheaper materials, more particularly the windows, than those used for the first protection. 
     It is understood that the description and illustration just given hereinabove of the method, device and machine-tool are given for the purpose of disclosure and not limitation. It is obvious that various arrangements of, modifications and improvements to the example here above will be possible without departing from the scope of the invention taken in its broadest aspects and spirits. 
     In order to permit better understanding of the drawings, a list of the reference symbols with their explanations is presented here below. 
       100  . . . Lengthening travel device 
       110  . . . Part-carrying clamping subset 
       120  . . . Driving subset 
       121 , 122  . . . Guide rails 
       130  . . . Protection cover of guide rails 
       140 , 150  . . . swarf discharge device 
       160  . . . Main orifice of swarf discharge 
       200  . . . Tool-carrying ram 
       300 , 300 ′ . . . Storage device 
       400  . . . Outer cover 
       410 , 420 , 430  . . . Opening accesses of the outer cover 
     M . . . Machining machine-tool as a whole 
     P 1  . . . Machining station 
     P 2  . . . Driving station 
     P 3  . . . Control station