Abstract:
An expansion device for hollow bodies, such as pipe ends having a base body ( 1 ) in which a bore ( 11 ) for the axial guidance of a displaceable, a tapering spreading member ( 10 ) is disposed, and having an expansion head ( 13 ) which contains a thimble ring ( 14 ), and sector-shaped spreader jaws ( 15 ) and is releasably joined to the base body ( 1 ). The spreader jaws ( 15 ) are guided for radial displacement in the thimble ring ( 14 ) by the axial movement of the spreading member, and friction surfaces are provided with a coating of a hard material to reduce attrition. In one embodiment at least the portion of the spreading member ( 10 ) that acts upon the spreader jaws ( 15 ) is provided with a coating ( 18 ) made of the hard material, e.g., titanium nitride (TiN).

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to an expansion device for hollow bodies.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     On account of the very complex geometric and friction conditions, which are explained at length in the detailed description, the spreading member in particular is subject to high and irregularly distributed stresses which definitely shorten the desired service life of the device.  
         [0003]     An expansion device of the kind in question of the plier type has been known since 1970 through U.S. Pat. No. 3,550,424. The document deals with the problem that enormous internal stresses are produced in the manual device and that to overcome them a staged drive is to be used for the hand lever so as to reduce the manual stresses. But it is not the stresses involved in the system and the resultant wear that are reduced thereby, but the far greatest part of such stresses are caused by steel-on-steel friction. Since about the same time such devices have come on the market world-wide in great numbers.  
         [0004]     Through DE 38 26 187 A1, in the course of the further development of such expansion devices a likewise generic expansion tool with a toggle lever drive and an adjustable adapter ring has become known. Due to the adapter ring it is possible to even out the influence of axial tolerance errors, but in the range between the spreading member and the spreader jaws and the wear produced therein, this has no influence, however, on the stresses in the area between the spreading member and the spreader jaws and the wear they cause, and no attrition-reducing surface coating is disclosed.  
         [0005]     In the RÖMPP CHEMIE LEXIKON, Georg Thieme Verlag Stuttgart, New York, 1995, vol. T-Z, pages 4631-4632, under “Titannitrid,” (titanium nitride) it is known in the prior art to use this material for thin layers, as a hard substance for protection against wear on fine machine bearings, antifriction bearings, cutting tools and the like and for lining reaction vessels for molten metals and for coating watch cases and decorative goods. In the cases last mentioned, the gilt look of the coating is probably a deciding factor. Nothing is said about its use in the case of complex conditions of stress and friction between the critical parts of expansion devices.  
         [0006]     DE 103 43 869 B3 discloses a standing device for an expansion lance of unspecific length for tubular hollow shapes, in which a hydraulic liquid, a so-called fluid, expands the expanding lance. The latter is held perpendicular in a clamping and holding device, which is arranged preferably in one piece, over a pressure distributing block with an introduction top. The introduction top has a through bore whose upper end is widened by a first conical surface and forms an insertion aid. At the bottom end of the expansion lance a double cone is held by means of a cap nut, the lower conical part cooperating with a second conical surface which is likewise arranged in the pressure distributing block, which thus has two hollow conical surfaces. The entire combination of convex and conical surfaces forms nothing more than a liquid-tight high-pressure connection within the stationary apparatus. For the creation of high resistance to pressure and attrition it is stated that the pressure distributing block can be provided with a hard surface coating of, for example, titanium nitride. However, no transition from surface pressure on edges or linear pressures takes place at the contact surfaces. Also, the surfaces in contact in the area of the titanium nitride coating do not participate in the expansion process but form only a pressure-resistant coating. Such a device is neither provided nor suitable for a hand tool.  
         [0007]     It is known through DE 26 54 102 C2, in the case of a replaceable expansion head, to provide a screw cap and the expansion jaws at the places at which friction occurs, with a slippery coating, such as hard chromium for example. This recommendation, however, disregards the fact that, in the case of the frequently expensive basic apparatus which is designed for a plurality of different and also accessory expansion heads, an often greater wear occurs, especially when expansion jaws coated accordingly, are in frictional engagement with the unprotected spreading member of the basic unit. The protective coating of a component of a pair of parts in frictional engagement always conflicts with an unprotected component, especially when the latter is especially endangered due to its slender geometry.  
         [0008]     It is to be noted in this case that such apparatus have been on the market since the middle of the 1960&#39;s, i.e., about 40 years. The visible parts, including the screw cap or sleeve, which are visible externally and under stress are already always chrome-plated, and mainly for reasons of appearance, in conjunction with protection against contact with the hand and with other tools or tool kits of craftsmen. In those days pipe connections were still made mainly threaded couplings and threading dies. Expansion technology, however, has become much more widespread in recent years. The hidden or barely visible parts, such as the spreading member and its completely concealed internal guidance are still uninfluenced thereby. The inventor has found that this is an obstacle in the way of the increasingly wide use of expansion technology. The economic success of the present invention is a credit to the inventor.  
         [0009]     It is therefore the object of the invention to present an expansion device as described above, by which, in spite of its very complex geometric shape and friction conditions which are explained in detail in the description, the service life and life expectancy of the expansion device and especially of the spreading member of the system is clearly prolonged.  
         [0010]     The present invention provides a solution of the aforementioned problem.  
         [0011]     The aforementioned problem is completely solved by the present invention. In particular, an expansion device as described above is provided by which, despite its very complex geometric shape and friction conditions, which are explained at length in the detailed description, the service life of the expansion device and especially of the spreading member of the system is definitely lengthened.  
         [0012]     As a result of further development of the invention, it is especially advantageous if, either individually or in combination:  
         [0013]     the hard material consists of titanium nitride (TiN);  
         [0014]     the coated surface of the spreading member is a conical surface;  
         [0015]     the spreading member is replaceably fastened to a driving bar which is mounted in the bore of the base body;  
         [0016]     the inside surfaces of the spreader jaws are configured as sectors of a conical surface and are likewise coated with the hard substance; and  
         [0017]     the coating is made by a method from the group of the physical (PVD), chemical (CVD) and physicochemical (PCVD) gas phase depositions. 
     
    
       [0018]     Examples of embodiments of the invention, their manner of operation, and additional advantages are further explained below with reference to FIGS.  1  to  4 .  
         [0019]      FIG. 1  is a partial axial section and an exploded representation of the drive end of a first embodiment of an expanding hand plier;  
         [0020]      FIG. 2  is section of  FIG. 1  on an enlarged scale and in a complete axial sectional representation;  
         [0021]      FIG. 3  shows an axial section taken through a tube end enlarged and expanded with the device according to  FIG. 2 ; and  
         [0022]      FIG. 4  shows a section similar to  FIG. 2  through a second embodiment, but with a coated spreader cone interchangeable with a driving bar on the housing side. 
     
    
     DETAILED DESCRIPTION  
       [0023]     In  FIG. 1 a  basic body  1  is shown which forms a guide housing to which is fastened a first hand lever  2  extending away in a radial plane. Parts  1  and  2  can also be made as a contiguous unit. The basic body  1  has two projecting fork parts  3  formed therefor t, of which only the back fork is shown. A pivot pin  4  passes through the fork parts  3  and its axis vertically intersects the system axis A-A. A second hand lever  5  is articulated on the pivot pin  4  between the fork parts  3 , which has a slot-like recess  5   a  of its own between the fork parts  3 . Between the hand levers  2  and  5  is disposed a downstop  6 , which consists of a threaded shaft  6   a  and a cap nut  6   b  with knurling  6   c . The mounting of the downstop  6  can optionally be done in the hand lever  2  or in the base body  1 .  
         [0024]     The recess  5   a  is penetrated in turn by a pivot pin  7  which can be rotated by turning the hand lever  5  around the pin  4 . The pivot pin  7  bears within the recess  5   a  a toggle lever  8  which acts, through an additional pin  9  vertically intersecting the system axis A-A, on a spreading member  10 . The pivot pins  4 ,  7  and  9  are disposed parallel to one another. The spreading member  10  contains three sections, namely another fork-like section  10   a  in the wings of which the axis pin  9  is journaled, a cylindrical section  10   b , and a spreading section  10   c  which causes the spreading action described below. The spreading member  10  is guided in a bore  11  in the basic body  1 , which is coaxial with system axis A-A. The toggle lever serves both for the expanding and for the positive withdrawal of the spreading member which the spreader jaws follow in the transverse direction.  
         [0025]     The basic body  1  bears on an external screw thread  1   a  of its own ( FIG. 2 ), an adapter ring  12  coaxial with the system axis A-A, having an external screw thread  12   a  and knurling  12   b . Spreading section  10   c  of the spreading member  10  which is shown as having a cone shape in the figures, is axially movable out of the basic body  1  and adapter  12  under the effect of the toggle lever  8 . Spreading section  10   c  of spreading member  10  has an increasing or decreasing cross-section corresponding to extension or retraction forces applied thereto. Spreading section  10   c  may be of any suitable shape, typically conical or pyramidal form, and cooperates with essentially complementary contact faces of the jaws. Due to contact with the pipe, spreading section  10   c  typically receives the most wear of any part of the device. The downstop  6  prevents the pins  4 ,  7  and  9  from getting into an outstretched position in which the stresses, of course, approach infinity.  
         [0026]     An expansion head  13  can be replaceably threaded on the basic body  1  and it, has a thimble ring  14  and a set of identical sector-shaped spreader jaws  15  guided radially within the thimble ring  14 . By way of example, six spreader jaws  15  whose outer surfaces in their outspread position assume the form of a cylindrical surface with a diameter D, while radial gaps  16  are opened between the spreader jaws. This diameter D determines the inside diameter of a widened or expanded end of a pipe  17  ( FIG. 3 ). The adapter  12  can be omitted if the object is to provide the basic body with a smaller expansion head  13 . In such a case the expansion head  13  is threaded directly onto the thread on the basic body  1 .  
         [0027]     Spreader jaws  15  have on the inside sector-shaped conical surfaces which are only in a single and very specific position with respect to one another in a common conical or envelope surface. The reason for this lies in the process of the manufacture of the workpiece, e.g., machining or precision casting. The workpiece is afterward sawn through diametrically or axis-parallelly with deliberate loss of material so that the above-mentioned radial gaps  16  are formed. Furthermore, the expansion heads  13  and the depth to which they are threaded onto the basic body  1  are subject to tolerances.  
         [0028]     Spreading member  10 , however, has but a single conical surface. As a result, when an expansion is performed, positions on the surface of the spreading member  10  have to be traversed involving linear and edge pressures with infinite values. Furthermore, when the pipe  17  is expanded, sliding movements also occur which take place with increasing stresses, because as the expanding material flows it solidifies due to the nature of the material, which results in great wear on the spreading member  10 .  
         [0029]     As seen by viewing  FIGS. 2 and 3  together, the conditions of force and friction at the free ends of the spreading member  10  and spreading jaws are especially critical. The greatest forces occur at very small contact surfaces or lines. Here, furthermore, those deformation forces from the area of transition  17   b  between the pipe  17  and the pipe end  17   a  add up at a point which is not supported by the spreading jaws.  
         [0030]     The result, however, is that the spreading member of the prior art has to be replaced more often, resulting, in the case of a one-piece spreading member, in complicated disassembly and reassembly of the device.  
         [0031]     The preceding part of this description applies to the state of the art; the description of the invention follows.  
         [0032]     A coating  18  is provided on the surface of the conical section  10   c  of the spreading member  10 , coating  18  is highlighted by thick lines and is made preferably of titanium nitride (TiN). Thus the service life of the expansion device is increased to a multiple, which is of special importance since repair at the point of use is, as a rule, impossible.  
         [0033]      FIG. 2  now shows, continuing the above numbering, additional details of the tool. Thus, it is shown that the coating of the spreading member can extend also onto the cylindrical section  10   b  of the spreading member. This has the further advantage that even the wearing effect of the transverse forces produced by the toggle lever  8  on the spreading member guiding means can be counteracted. It is furthermore shown that the spreading jaws are guided by rivets  19  in the thimble ring. The conversion of the axial motion of the spreading member  10  to radial motions of the spreading jaws is indicated by arrows.  
         [0034]      FIG. 3  shows, as already indicated above, an axial section taken through a pipe end  17   a  which has been widened or expanded with the device shown in  FIG. 2 . An unexpanded pipe  17  is to be inserted into this pipe end and soldered there. During the diametrical enlargement the inside surface of the pipe  17  slides due to the enlargement of the circumference onto the external surfaces of the spreading jaws  15 . It is, therefore, an additional advantage to provide these external surfaces and, if desired, also the inside surfaces of the spreading jaws, with the aforesaid hard coating.  
         [0035]      FIG. 4  shows an axial section similar to  FIG. 2 , but with the difference that the spreading member  20  consists of a conical part coated likewise to withstand attrition, which is threaded replaceably by means of a threaded connection into a driving rod  22  on the housing side. Into the basic body  1  a transition piece  23  is threaded by means of a threaded connection  24  and has a transition piece  23  with a cylindrical recess  23   a  into which the end of the spreading member  20  can be withdrawn. This embodiment has the additional advantage that, if the driving rod  22  is made accordingly, an uncoated spreading cone can be replaced with a spreading member  20  coated pursuant to the invention, which also permits retrofitting.  
         [0036]     The spreading member  20  can be driven by a toggle lever not shown here, or by a combination of rack and pinion, or by a cam. It is also possible, however, to provide an electromechanical or electrohydraulic driving device.