Abstract:
A handheld pressing tool, which is suitable in particular for crimping press fittings and/or cable lugs, has at least two pressing elements which can move in relation to one another. These can be closed by a hydraulically operated piston element. To this end, the piston element is connected to at least one actuation element for moving at least one of the pressing elements. When the piston element is being returned to a short-stroke starting position, a brake element acts on the piston element and/or the actuation element.

Description:
BACKGROUND 
     1. Field of the Disclosure 
     The disclosure refers to a handheld pressing tool that is suited in particular for the crimping of press fittings or cable lugs. 
     2. Discussion of the Background Art 
     Handheld pressing tools comprise an electro-hydraulic drive for example. Here, an electromotive drive means operates a hydraulic pump that moves a piston element. The piston element is connected with an actuating element such as a roller head. To close at least two pressing elements that are movable with respect to each other, i.e. to effect crimping, the actuating element acts upon at least one of the pressing elements. With tongs-shaped pressing elements, two pressing elements are pivotably provided on the handheld pressing tool, the actuating element, which in particular comprises a roller head, acting on both pivoting arms of the pressing elements. The displacement of the piston element, and thus of the roller head, in the longitudinal direction causes the two pivoting arms to be pushed apart. Since the two pressing elements are pivotable about a pivot axis, pushing the pivoting arms apart causes the closing of the ends of the pressing elements carrying or forming the pressing jaws. Depending on the stroke length of the piston element, handheld pressing tools are respectively suited for different pressing elements, with the pressing elements being moved over a longer pressing distance if the stroke is large. This is the case, for example, when such pressing elements are used to crimp press fittings with a large outer diameter. It is necessary in this case to open the two tongs-like pressing elements wide in order to place them around the press fitting having a large outer diameter. When such handheld pressing tools with a small stroke are also used for press fittings with a smaller outer diameter, for example, this has the consequence that the press fitting is crimped only in the last part of the pressing stroke. Thus, there is a large idle stroke. This has the disadvantage that a relatively long crimping time is required for the crimping. 
     To allow the use of a handheld pressing tool to perform crimping both with a required large stroke and with a required short stroke by means of different pressing elements, a pressing tool with an adjustable stop is known from DE 10 2006 003 044. For this purpose, the pressing tool described in DE 10 2006 003 044 has a stop displaceable in the longitudinal direction of the piston element. The same can be positioned by the user in different end positions. Prior to a crimping operation, the user thus has to displace the end stop manually in the longitudinal direction for adjustment. This has the disadvantage that the user has to decide prior to each crimping operation, what stroke the pressing device is operated with. This represents a considerable effort and bears the risk of erroneous operations. 
     It is an object of the disclosure to provide a handheld pressing tool with which different crimping strokes can be realized in a simple manner, depending on the pressing elements used in the pressing tool. 
     SUMMARY 
     The handheld pressing tool of the disclosure, which is in particular suited for the crimping of press fittings and cable lugs, comprises at least two pressing elements movable relative to each other. The pressing elements carry the pressing jaws or are formed integrally with the pressing jaws. Preferably, the pressing elements are two tongs-like elements which are connected with a housing of the handheld pressing tool via an in particular common pivot axis. A hydraulically operated piston element is provided for moving at least one of the two pressing elements. In order to drive, i.e. to move, the piston element in the longitudinal direction to perform a crimping operation the piston element may be actuated through a hydraulic pump that is driven by an electric motor, for example. When the crimping is accomplished, the piston element is returned to the starting position by moving the pressing jaws of the pressing element apart. 
     At the end directed towards the pressing elements, the piston element has at least one actuating element for moving at least one of the pressing elements. According to the disclosure a brake element is provided that acts upon the piston element and/or the actuating element when the piston element is returned. According to the disclosure the brake element is designed such that the piston element is first returned to a short-stroke starting position. This is a starting position from which the piston element performs only a relatively short stroke to close the pressing elements. When the handheld pressing tool is used in the short-stroke starting position, it is used, for example, to crimp press fittings with relatively small diameters. 
     In a preferred inventive development of the handheld pressing tool the brake element can be overcome in order to return the piston element to a long-stroke starting position. This is possible in particular, because, when corresponding pressing elements are used that require a long stroke, the pressing jaws of the press elements are pushed further apart, in particular manually. According to the disclosure, the piston element is then automatically pushed back to the long-stroke starting position. According to the disclosure, this is particularly advantageous, since the spreading or opening of the pressing jaws, which is indispensible in the preparation of a crimping process, automatically causes the piston element to be pushed back to the long-stroke starting position. According to the disclosure, it is not required in this context to make any adjustment to the pressing tool. In particular, no stop needs to be adjusted. Thus, the operation of the pressing tool is simplified and erroneous operations are avoided. 
     Preferably, the brake element exerts a braking force on the piston element and/or the actuating element. A retaining element may be provided for this purpose, the retaining element preferably being spring-loaded. In this context it is possible to provide a separate spring, such as a coil spring, cooperating with the retaining element and/or to design the retaining element so as to be resilient or to connect it resiliently with a housing of the handheld pressing tool. Due to the provision of such a retaining element, it is possible to return the piston element to the long-stroke starting position in a simple manner, since the brake element is overcome by simply opening the pressing elements. In particular, the retaining element is compressible and/or radially displaceable for the purpose of returning the piston element to the long-stroke starting position. For example, the retaining element is pushed back into the housing of the handheld pressing tool in order to overcome the braking force. This may be done in particular by means of the pivoting arms of the pressing elements. 
     Preferably, the actuating element comprises a roller head. Especially, when two pressing elements are provided, it is preferred that the roller head has two rollers, each of the rollers respectively acting on one of the pressing elements, specifically on the respective pivoting arm of the pressing elements. Thus, a displacement of the piston element in the longitudinal direction thus causes the two pivoting arms to be pushed apart via the rollers that contact the pivoting arms. Owing to the fact that they are supported by a pivot axis connected with the housing of the pressing tool, the in particular opposite pivoting arms cause the pressing jaws to be pressed together. Here, it is particularly preferred that the pivoting arms have convexly curved opposite flanks. 
     Preferably, the actuating element, and thus the piston element, is returned by opening the pressing elements, wherein the return to the short-stroke starting position is assisted by a spring element or is exclusively performed by a spring element. The brake is always overcome by opening the pressing elements still farther so that the actuating element and the piston element are automatically returned to the long-stroke starting position, whereby the braking force exerted by the braking element is overcome. 
     The following is a detailed description of the disclosure with reference to a preferred embodiment and to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the Figures: 
         FIG. 1  is a schematic partly sectional side elevational view of a part of a pressing tool in a closed position, with pressing elements arranged therein that require a short pressing stroke, 
         FIG. 2  shows the pressing tool illustrated in  FIG. 1 , with the pressing elements opened, 
         FIG. 3  shows a schematic cross section of the pressing tool along line III-III in  FIG. 2 , with no pressing elements being illustrated, 
         FIG. 4  is a schematical longitudinal section of the pressing tool corresponding to the view in  FIG. 2 , with pressing elements being provided that require a long pressing stroke, and 
         FIG. 5  is a schematic cross section of the pressing tool along line IV-IV in  FIG. 4 , with no pressing elements being illustrated. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The Figures each illustrate only the front part of the pressing tool which is relevant to the disclosure and which holds the pressing elements. 
     A piston element  10  is arranged in a housing  12  of the handheld pressing tool and is displaced in the longitudinal direction  14  by a hydraulic pump not illustrated in detail. The hydraulic pump is operated by an electromotive drive device which also not illustrated herein. The piston element  10  is connected with an actuating element which in the embodiment illustrated comprises a roller head  16 . The roller head  16  comprises two rollers  18  that are illustrated in section in  FIG. 1 . 
     Further, two pressing elements  20  are pivotably supported in the housing  12  by a respective pivot axis  22 . The pressing elements  20  illustrated in  FIG. 1  are pressing elements that can be operated with a short stroke. Each of the two pressing elements  22  is formed integrally with pressing jaws  24 , which pressing jaws  24  serving to crimp a press fitting, for example. 
     After the crimping of a press fitting or the like, the pressing elements  20  are in the closed position illustrated in  FIG. 1 . In this state the crimping is terminated. In  FIG. 1 , the piston element is also already pushed back to the short-stroke starting position. In the embodiment illustrated herein, this is effected by means of a spring  21  which urges the piston element  10 , together with the actuating element  16 , back to the short-stroke starting position. Thereby, the hydraulic liquid is pressed back into a hydraulic reservoir, for example. For a displacement of the piston elements  10  in the longitudinal direction  14 , the hydraulic liquid is supplied from the hydraulic reservoir by means of the hydraulic pump not illustrated herein. 
     To perform a new crimping operation using the pressing elements  20  requiring a short stroke, the pressing elements  20  are opened manually. This is done by pushing the two pressing jaws  24  apart or by pressing pivoting levers  26  of the two pressing elements  20  together. Thereby, the pressing elements  20  are moved to the starting position illustrated in  FIG. 2 . For the next crimping operation and thus for the closure of the two pressing elements  20 , the piston element  10  is again displaced in the direction of the arrow  14  by means of the hydraulic pump. Thus, the two rollers  18  of the roller head  16  come to contact the two flanks  28  of the pivoting arms  26  and push the pivoting arms  26  apart. Thereby, the two pressing elements  20  are pivoted about the pivoting axis  22  and the pressing jaws  24  are closed. 
     Owing to the provision of a brake element  30  ( FIG. 3 ), the pushing back of the piston element  10 , which in the embodiment illustrated in  FIGS. 1 to 3  is effected by a spring  21 , occurs only up to a short-stroke starting position. For this purpose, the brake element  30  comprises a retaining element  32 . The retaining element  32  comprises a spring-loaded ball  34 . The latter acts on a support element  36  of the roller head  16  such that the roller head  16 , and thus the piston element  10  connected with the roller head  16 , is slowed down in the short-stroke starting position illustrated in  FIG. 3 . 
     In particular for the purpose of avoiding a canting of the roller head  16 , two opposite brake elements  30  are provided in the embodiment illustrated. The two brake elements  30  are identical in design. 
     To be able to cause the piston element  10 , together with the roller head  16 , farther backwards in the direction of the arrow  38 , the two retaining elements  32  are each movable in the direction of the arrow  40  or can be pushed into the housing  12 . The movement in the direction of the arrows  40  occurs in particular against a spring force, while it is also possible that the movement is effected by an elastic deformation of the retaining elements  32 . 
     Such an overcoming of the braking effect of the brake elements  30  is necessary and suitable to allow the mounting of pressing elements  42  ( FIGS. 4 a  to 4 c   ) into the pressing tool that require a longer stroke. 
     Pressing elements  42  with a long stroke ( FIG. 4 a   ) are used as the pressing tool, with the pressing tool still being in the position for short-stroke pressing elements and, thus, the brake element  30  still acts on the actuating element  16 . By opening the pressing elements  42 , the two flanks  46  of the pivoting levers  26  come to contact the two rollers  18  of the roller head  16  ( FIG. 4 b   ), with the braking force of the brake element  30  being overcome by opening the pressing elements further ( FIG. 4 c   ). After the braking force of the brake element  30  has been overcome, the spring  21  thus causes the piston element  10 , together with the actuating element  16 , to be fully withdrawn to the long-stroke position. 
     Replacing the pressing elements  20  with the pressing elements  42  is done by retracting a locking element  43  ( FIG. 3 ) in the direction of the arrow  44 . Thereafter, the pressing elements  20  can be removed from the pressing tool and the pressing elements  42  can be inserted into the pressing tool. The insertion of the pressing elements  42  causes flanks  46  of the two pivoting arms  48  of the pressing elements  42  to press on the rollers  18  so that these are pushed back further in the direction of the arrow  38  ( FIG. 3 ) against the action of the two brake elements  30 . Thus, in  FIG. 4 c   , the roller head  16  and the piston element  10  are in the long-stroke starting position. To close the pressing jaws  50  of the pressing elements  42 , the piston element  10  is again displaced in the direction of the arrow  14  by operating the hydraulic pump. 
     As can be seen in particular in  FIG. 5 , the retaining elements  32  of the brake elements  30  are in a retracted position and, as such, respectively contact an outer face  52  of the support element  36 . 
     In an alternative embodiment of the brake elements  30 , these are arranged completely inside the housing  12 . The brake elements also comprise retaining elements  58  loaded by a spring  60 , the spring  60  exerting a force acting inward in the direction of the piston element  10 . The retaining elements  58  are pushed back against the force of the springs  60 .