Centering device for a spring core mounting machine
BACKGROUND OF THE INVENTION 
     The present invention relates to a centering device for centering adjacent helical springs, and more particularly to a centering device for a spring core mounting machine. 
     Spring core mounting machines are used to construct the inner spring cores for inner spring mattresses and spring supports for mattresses. These spring cores have a large number of springs of helical configuration which are mounted side by side, with the terminal windings of the springs at the upper and lower ends thereof being connected, usually by threading a small helical connecting spring around portions of two adjacent ones of the helical support springs. 
     A spring core mounting machine for making spring cores of the type here in question is described in German Patent Number 1,552,149 and in the thereto corresponding U.S. Pat. No. 3,516,451. This machine uses support springs which do not have the bent-out portions in their terminal convolutions. In many instances, the helical support springs which are used to make up the spring core have in their terminal windings two diametrically oppositely located portions at which they are bent out, with these portions extending approximately in a straight line and parallel to one another. Helical springs with such bent out portions or zones are already known as &#34;offset springs&#34;. 
     The centering device according to the present invention is intended to be used with this type of machine, i.e. to make it possible to use in this type of machine the so called offset springs having the bent-out portions in their terminal convolutions. To be able to use this type of spring in this type of machine, it is necessary to center the individual springs on insertion thereof into the associated pair of clamping jaws provided for holding the springs, i.e. to so orient these springs that the bent-out portions of the terminal convolutions of adjacent springs which are to be connected with one another are located precisely opposite one another and in abutment or almost in abutment. 
     SUMMARY OF THE INVENTION 
     It is therefore the general object of the present invention to provide a centering device for use in the aforementioned spring core mounting machine, which allows the spring core mounting machine to be used with offset springs. 
     A more particular object of the invention is to provide a centering device for use with the aforementioned spring core mounting machine which assures that offset springs are automatically centered prior to the connection of their terminal convolutions by means of connecting helixes. 
     In keeping with these objects, and with others which will become apparent hereafter, one feature of the invention resides in a centering device for centering adjacent helical springs during connection of their terminal convolutions in a machine for making inner-spring cores, the terminal convolutions each having two diametrically opposite bent-out sections and the machine including at least one set composed of a stationary jaw and a movable jaw movable toward and away from the stationary jaw in a path, and at least one slide reciprocable in said path and having a surface engageable with a terminal convolution of a respective newly supplied spring for pressing it against the movable jaw. Briefly stated, such a centering device may comprise a centering recess in the aforementioned surface adapted to center the respective terminal convolution and including a depression shaped to receive a bent-out portion; and a spring-biased hook portion at a leading end of the slide engageable with a respective terminal convolution for drawing the same in the aforementioned path away from the movable jaw and towards the stationary jaw, each of the jaws having a centering recess for a respective one of the bent-out portions. 
     By resorting to the device according to the present invention, a first centering is effected during the advancement of the slide by the centering phase of the same, whereas a subsequent or final centering is effected, if necessary, during pushing of the spring into the stationary jaw. 
     The invention will hereafter be described with reference to the embodiment as shown in the appended drawing. It is to be understood, however, that the drawing is one embodiment only and that it is not to be considered limiting of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a side view, illustrating in a somewhat diagrammatic partly sectioned manner those parts of the centering device and spring core mounting machine which are necessary for an understanding of the invention; 
     FIG. 2 is a top-plan view of FIG. 1; 
     FIG. 3 is a view similar to FIG. 2 but illustrating the machine in a different operating position; 
     FIG. 4 is a view similar to FIG. 3, illustrating still a further operating position; 
     FIG. 4a is a detailed view, seen from the top, showing adjacent terminal sections of two springs being connected by a connecting helix; and 
     FIG. 5 is a view similar to FIG. 4 showing still an additional operating position. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawing in detail it should first be understood that the details of the spring core mounting machine with which the centering device according to the present invention is to be used, are disclosed in the aforementioned German Patent 1,552,149 and the thereto corresponding U.S. Pat. No. 3,516,451, the latter being incorporated herewith by reference. 
     With this in mind, it will be seen that FIGS. 1 and 2 show only a stationarily mounted transverse bar 1 on which a support or carrier is secured to which a stationary clamping jaw 3 is mounted. A second clamping jaw 4, movable by not illustrated means which are known per se into and out of the open position of FIGS. 1-2 from the closed position shown in FIG. 4a, is also carried by the support 2. 
     A slide 6 is mounted on a traverse 5 and is shiftable lengthwise of the support 2. It will be understood, of course, that although the drawing shows only a single set of jaws 3,4 and a single slide 6, an entire series of sets of jaws and of slides will be provided which are arrayed next to each other (i.e. in a row behind the ones shown in FIG. 1) and which are all operated at the same time so as to be able to produce a spring core. However, it is not necessary for an understanding of the invention to show all these various elements, and therefore they have been omitted. 
     FIG. 2 shows best the configuration of the upper and lower terminal windings of the so called offset springs 7, i.e. the inner springs which are to make up the spring core. The terminal windings of these springs 7 each are provided at two diametrically opposite locations with bent-out portions 7b in which the wire of the spring extends in a straight line or at least approximately in a straight line, with the portions 7b at opposite sides of the convolution extending in parallelism with one another. In these portions 7b, the terminal windings (at the upper and at the lower ends) of two adjacent springs 7 are connected in known manner by threading a wire helix 17 through them (compare FIG. 4a). 
     The springs 7 are placed between the open clamping jaws 3,4 in approximately centered position, either by hand or by the pivot arm 8 of a transfer machine. In order to obtain an exact centering, the following measures are provided according to the present invention: 
     The slide 6 is provided at its surface cooperating with the terminal windings 7a, 7b with a surface which is inwardly curved at 6a and provided with a recess 6b for the portion 7b, this surface acting as a centering surface. In addition, the slide 6 is provided with a lever 10 which is pivotable about a horizontal axis 9 and which has at its front end a pull-back hook 11; the other end of the lever 10 is biased by a spring 12 to tilt about the axis 9 so that the hook 11 is always urged in clockwise direction (FIG. 1), i.e. is always urged to its operating or effective position. The slide 6 with the lever 10 is covered by a cover sheet 13. 
     As illustrated by the arrow 14 in FIG. 2, the slide 6 performs a (forward) movement to the position shown in FIG. 3, causing the terminal convolution 7a to be pressed against the terminal convolution 7a of the preceding spring in the clamping jaw 4. The curved contour 6a of the surface of slide 6 causes the terminal convolution 7a to be centered during this movement and at the same time the hook 11 snaps over and engages the terminal convolution in the portion 7b. Thereupon the slide 6 moves in the opposite direction, as indicated by the arrow 15 in FIG. 3, and the hook 11 now pulls the terminal convolution 7a into the position shown in FIG. 4 so that it enters into the depression provided for it in the stationary clamping jaw 3, obtaining an additional centering effect thereby. 
     Now, the movable clamping jaw 4 is moved to closed position, as shown in FIG. 4a and in known manner a wire helix is threaded about the portions 7b, 7b of the two adjacent springs 7, connecting the terminal convolutions 7a of the two adjacent springs 7. The clamping jaw 4 is then opened again (FIG. 4) and the connected zone of the two terminal convolutions is lifted in known manner. The slide 6 then performs a further movement in the direction of the arrow 16 as shown in FIG. 4, whereby the still free second bent-out portion 7b of the terminal convolution 7a is moved into the opened clamping jaw 4, and thereupon the hook 11 is released in any convenient manner and the slide 6 is returned to its position shown in FIG. 2, so that a new working sequence can begin, in which a new spring is moved to the position of FIGS. 1 and 2. 
     The invention has been described hereinbefore with reference to an exemplary embodiment and is illustrated in the drawing. It is to be understood, however, that this is only to facilitate an understanding of the invention and that the scope of protection sought is defined exclusively in the appended claims.