Patent Publication Number: US-8985186-B2

Title: Casting device for a piston for an internal combustion engine and method for opening and/or closing a casting device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 of PCT/EP2011/070454 filed Nov. 18, 2011, which claims priority from DE 10 201 0 064 078.6 filed on Dec. 23, 2010, the disclosures of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention is directed toward a casting device for a piston for an internal combustion engine as well as a method for opening and/or closing a casting device. 
     2. Related State of the Art 
     When casting pistons for internal combustion engines, one particular challenge is to form the piston with as few lost cores as possible in a form that has to be reworked as little as possible and has been optimized as regards savings in weight. 
     To form grooves below the ring zone of the piston, it is known from DE 199 22 809 A1 to provide, along with a linearly displaceable sleeve, a pivotal core for the formation of such a groove. 
     According to US 2008/0257518 A1, suitable cores for the formation of the grooves below the ring zone, which are used as cooling grooves, are displaced for the most part linearly and obliquely as regards the sleeves. 
     SUMMARY OF THE INVENTION 
     A simplified device and a method for casting a piston for an internal combustion engine is provided. Such allows, to the extent possible the formation of recesses to save weight. 
     Accordingly, this device comprises at least one, mostly linearly displaceable sleeve for the formation of at least one piston pin bore. The sleeve is therefore a component that comprises at its end directed at the casting space an essentially cylindrical portion that leaves a space for the piston pin bore on the finished piston. In particular, the sleeves can have on the portions facing away from the casting space sections with a larger diameter, and the sleeves can comprise measures for coupling with a drive or, as described below, for coupling at least indirectly with the slider. 
     With the casting device as according to the invention, at least one slider displaceable mostly linearly and obliquely towards the sleeve is provided namely for formation of at least one recess below the ring zone on the piston. The path of displacement of the slider is a result of the fact that the recesses below the ring zone typically extend below an acute angle towards the piston axis and thus extend obliquely towards the axis of the sleeves extending perpendicular to the piston axis. The sleeve is at least indirectly coupled to the slider such that during displacement the sleeve entrains the slider at least in part. This coupling can be formed during the opening of the casting device, for example, such that the sleeve is initially retracted at least a short distance, and then a section on the sleeve engages at least indirectly with the slider such that this is displaced obliquely towards the sleeve. In other words, the sleeve is coupled in particular for the opening movement in such a manner to the slider that it “entrains” this as part of a pulling movement. Moreover, this coupling can also be effective during closure as part of a “pressing” movement. 
     When closing the casting device, the operation can be carried out essentially in reverse, with it presently being preferred to effect a movement of the slider back into its closed position over substantially the entire closure movement of the sleeve. The slider expediently has a projection that forms the positive form of the desired recess and is designed to broaden in the movement direction for a particularly simple retraction during opening of the form. The casting device also comprises any form (halves) that are required for casting a complete piston. Furthermore, both the sleeves as well as the slider are provided preferably twice in order to form the necessary configurations on both sides of the piston. Finally, the sleeve can extend through an opening in the slider. Advantageously, conventional casting devices do not have to be re-configured. There is furthermore the advantage over a pivoting movement of casting cores for formation of recesses below the ring zone that the recesses can be designed to be deeper, and by this a more extensive savings in weight is possible. 
     Preferably, the slider is guided in at least one guide. By this, the movement of the slider can be defined particularly exactly. At the same time the coupling with the sleeve can take place flexibly within a certain framework such that the guide can be designed to be exchangeable and/or variable, for example with regard to the angle, without having to change the coupling with the sleeve. 
     Accordingly, it is furthermore preferred that the guide is exchangeable. This offers the advantage to be able to adjust the path of displacement of the slider to the various piston geometries. Alternatively or supplementing this, the angle provided by the guide can be variable as regards the displacement path of the sleeve. 
     For the coupling between the sleeve and the slider, what is called a pivoting fork is presently preferred, with which the slider is at least indirectly connected and is pivotably connected at least to a certain extent. For this, the pivoting fork can be pivoted by the sleeve such that the sleeve “entrains” the slider by means of the pivoting fork. 
     In particular in view of the possibility to alter the displacement path of the slider by exchanging at least one guide and/or setting a different angle, it is advantageous if the slider is furthermore coupled displaceably at least to a minor extent to the pivoting fork. 
     In view of the coupling between the sleeve and the slider by means of the pivoting fork, presently at least a peg on the sleeve is furthermore preferred which can made to engage with a projection and/or a sliding surface on the pivoting fork. The engagement with a projection is presently preferred for the entrainment during opening, while cooperation with a sliding surface during the closure movement offers advantages. 
     The solution of the above-mentioned object is achieved in addition by a method according to which a sleeve displaceable for the most part linearly entrains at least in part at least one slider that is displaceable mostly linearly and obliquely to the sleeve. The preferred further embodiments of the device can be applied to the method as according to the invention. Furthermore, any method features described in connection with the device can be used with the method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the invention shown as an example in the drawings will be explained below in which: 
         FIG. 1  shows a lateral view of a part of the casting device according to the invention; 
         FIG. 2  shows a first cut view of the casting device shown in  FIG. 1  in a closed condition; 
         FIG. 3  shows a second cut view of the casting device shown in  FIG. 1  in a closed condition; 
         FIG. 4  shows a first cut view of the casting device shown in  FIG. 1  in a condition of the sleeve retracted in part; 
         FIG. 5  shows a second cut view of the casting device shown in  FIG. 1  in a condition of the sleeve retracted in part; 
         FIG. 6  shows a first cut view of the casting device shown in  FIG. 1  in a condition of the sleeve retracted in full; and 
         FIG. 7  shows a second cut view of the casting device shown in  FIG. 1  in a condition of the sleeve retracted in full. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     In  FIG. 1 , a section of the casting device is shown, with in the first place a guide  14  for the linear movement of a slider  12  in the direction A being recognizable in the lateral view of  FIG. 1 . Furthermore, an area of the sleeve  10  displaceable in the direction B is recognizable in  FIG. 1 , which is turned away from the casting space (according to  FIG. 1  to the left). Therefore, the directions A and B are oblique in relation to each other. As will be explained in more detail below, the sleeve  10  and the slider  12  are coupled by means of a pivoting fork  16  that is pivotable about an axis  24  in a direction C. Said coupling is carried out in the example shown via a peg  18  that can be engaged during the opening with a projection  20  on the pivoting fork  16  and during closure with a sliding surface  22  on the pivoting fork. 
     Furthermore, it can be seen in  FIG. 2  that corresponds to the condition of  FIG. 1  that the sleeve  10  extends through an opening in the slider  12 , and that according to the figures the slider  12  has in the upper region a nose-like projection  26  for formation of a recess below the ring zone of a piston. 
     Furthermore, the coupling between the slider  12  and the pivoting fork  16  can be seen in  FIG. 3 , which consists in that a broadened, free end  28  of the pivoting fork  16  is placed in a space  30  in the slider such that a linear movement can be transferred, that further, as is recognizable from  FIG. 7 , a minor pivot movement is possible, and further a certain linear displacement is allowed (according to the figures from the right to the left). This movability is favorable owing to the determination of the movement of the slider by the guide (see  FIG. 1 ) since with said degrees of freedom between the slider and pivoting fork the movement of the slider can be defined by the guide, however, it can be transferred by the pivoting fork to the slider. 
     While  FIGS. 2 and 3  correspond to the closed condition of the casting device, and both the sleeve as well is also the slider are in a casting position, an intermediate position is shown in  FIGS. 4 and 5  in which the casting device is still closed, however the sleeve  10  is retracted in part while the slider  12  is still in a casting position. In  FIG. 5  it can be seen that the peg  18  on the sleeve just comes into engagement with the projection  20  on the pivoting fork  16  in order to begin the entrainment of the slider  12 . 
     The end position is to be found in  FIG. 6 , in which the sleeve  10  is retracted to its maximum extent, the slider is freely movable and the casting device can thus be opened. It can be seen from the position of the pivoting fork  16  that this was pivoted at least to a minor extent counter-clockwise, and has thereby entrained the slider, as is shown in particular in  FIG. 7 , the movement of which is still defined by the guide  14  (see  FIG. 1 ). Since in the example shown, the path of displacement of the slider is comparatively steep, the free end  28  of the pivoting fork  16  has moved slightly out of the space  30  of the slider  12 . 
     When the casting device, starting with the condition shown in  FIG. 7 , is supposed to be closed, the sleeve will be displaced again into the condition shown in  FIGS. 1 through 3 . The peg  18  slides hereby on the sliding surface  22  off of the pivoting fork which, as a consequence of this, returns the slider  12  to the fully retracted position.