Abstract:
A blind rivet setting device and method of operating the blind rivet setting device. The blind rivet setting device includes a housing, a pulling device that is at least partially arranged in the housing and a drive that acts on the pulling device in a pulling direction and in a reset direction oriented opposite to the pulling direction. A length of at least one of the housing and the pulling device is changeable from a first length to a second length when a predetermined force is exceeded.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority under 35 U.S.C. §119(a) of European Patent Application No. 14 158 483.9 filed Mar. 10, 2014, the disclosure of which is expressly incorporated by reference herein in its entirety. 
       BACKGROUND OF THE EMBODIMENTS 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the invention relate to a blind rivet setting device with a housing, a pulling device that is at least partially arranged in the housing, and a drive that acts on the pulling device in a pulling direction and in a reset direction oriented opposite to the pulling direction. 
         [0004]    2. Discussion of Background Information 
         [0005]    A blind rivet setting device of this type is known, e.g., from DE 41 26 602 A1. 
         [0006]    “Blind rivet setting device” is to be understood below as meaning a device that can be used to set blind rivets, blind rivet nuts, and blind rivet fasteners generally. To set a blind rivet fastener of this type, a pulling mandrel of the blind rivet fastener is inserted into the housing through a front-face opening. The blind rivet fastener is then guided through an opening in a component until the set head of the fastener bears against the component. When the drive of the pulling device is actuated in the pulling direction, the pulling mandrel of the pulling device is gripped and pulled in the pulling direction. The housing presses the set head against the component. As a result, a closing head forms on the side of the component facing away from the set head. When the closing head is formed and the setting operation is thus virtually complete, the drive drives the pulling device in the reset direction so that the device is once again moved in the direction towards the front-face opening of the housing. The pulling mandrel can then be removed from the housing and the pulling device, and the blind rivet setting device is available for a new setting operation. 
         [0007]    To achieve a highest possible productivity, it is desirable to have the movement of the pulling device during a setting operation and also the reset movement of the pulling device proceed as quickly as possible. The drive is therefore embodied or formed in an adequately powerful manner. To automatically control the movement, especially the reset movement of the pulling device, one or multiple sensors are used. 
         [0008]    The movement of the pulling device in the reset direction must occur with a certain precision. If the pulling device is not moved far enough in the reset direction, then a gripping device may not be opened far enough to remove a broken-off pulling mandrel or to allow a new pulling mandrel to be inserted. However, if the pulling device is moved too far, then it can damage the housing. 
         [0009]    Even with a control that guides the movement of the pulling device with the necessary precision, problems can occur. These problems result, for example, in that abrasion debris can be produced during the setting of a blind rivet fastener, which debris accumulates between the housing and the pulling device. A veritable “plug” can form here. If the pulling device is then moved back into its initial position, then the force applied to the housing by the drive via the pulling device and the plug can be large enough that damage results in turn, especially to the housing. 
       SUMMARY OF THE EMBODIMENTS 
       [0010]    Accordingly, embodiments of the invention reduce the risk of damage. 
         [0011]    A blind rivet setting device of the type named at the outset includes a housing and/or a pulling device that can be changed between a first length and a second length in the reset direction after a predetermined force is exceeded. 
         [0012]    With this solution, damage is avoided in that the pulling device shortens its length when a predetermined force is exceeded or the housing changes its length when a predetermined force is exceeded. Of course, both measures can also be combined. By the change in length, it is possible to alleviate the problem that would otherwise occur during the reset movement as a result of the application of an exceedingly large force between the housing and the pulling device. If, during the reset movement of the pulling device, a situation occurs, e.g., due to the aforementioned plug, in which the pulling device can no longer move back into its initial position because the accumulated debris prevents this, then no additional housing-damaging pressure is produced; rather, the pulling device is compressed or the housing is lengthened. The user can then take measures to eliminate the problem again, e.g., to remove the debris. In the pulling direction, however, the length is unchanged, i.e., precisely the desired kinematics, i.e., the interaction between the housing and the pulling device that results in the formation of the closing head of the blind rivet fastener, occur during a movement of the pulling device in the pulling direction. 
         [0013]    Preferably, the pulling device has clamping jaws that are loaded into a chuck housing by a compression spring. The further the clamping jaws are moved into the chuck housing, the more closely they approach one another. The compression spring is thus used to produce a clamping force with which the clamping jaws can grip a pulling mandrel that has been slid into the pulling device. The functioning of the compression spring remains uninfluenced by the possibility of the change in length. 
         [0014]    Preferably, the housing includes a nose piece. In a resting state, the clamping jaws are displaced into an opened position by the nose piece if the first length is present and are not displaced into the opened position if the second length is present. The clamping jaws are typically arranged in a chuck housing which, when it acts on the clamping jaws in the pulling direction, moves the clamping jaws towards one another perpendicular to the pulling direction, so that the clamping jaws can hold in place a pulling mandrel of a blind rivet fastener. The clamping jaws are thereby usually pressed into the chuck housing by the force of a spring. The nose piece projects into the chuck housing when the pulling device is located in its initial position, i.e., in the position moved furthest in the reset direction, so that the clamping jaws have been slid back a small distance in the chuck housing and are thus located in an “opened position,” in which a pulling mandrel can be removed from the clamping jaws or inserted into the clamping jaws. If fouling or contamination of the type described accumulates between the housing and the pulling unit, the embodiment described has the advantage that the user of the blind rivet setting device is alerted to a need for maintenance. If it is no longer possible to insert a pulling mandrel of a blind rivet fastener into the pulling device through the front-face opening, it is a natural reaction for the user to assume that fouling or the like is present. In this case, partial disassembly of the housing will enable the removal of the fouling. In this manner, the problem is essentially solved. In many cases, the user is already alerted to the fault in that it is no longer possible to pull the pulling mandrel of a set blind rivet fastener out of the housing without difficulty. 
         [0015]    Preferably, a difference between the first length and the second length lies within the range of 1 to 5 mm. The change in length is thus relatively small. However, it is sufficient to prevent exceedingly large forces from acting between the pulling device and the housing. 
         [0016]    Preferably, the pulling device includes a first pulling element and a second pulling element. The first pulling element and the second pulling element are positively engaged and an elastic element acts between the first pulling element and the second pulling element in the reset direction. With this embodiment, it is possible to transfer the force necessary to form the closing head of the blind rivet fastener from the drive to the pulling mandrel by means of a continuous pull rod. As a result of the positive engagement between the first pulling element and the second pulling element, an avoidance movement is not possible. This is not the case, however, for a movement in the opposite direction. Here, the second pulling element acts, possibly through one or multiple additional parts, on the first pulling element via an elastic element. Therefore, if the first pulling element reaches its limit at the housing, for example, even with an intermediate layer of an accumulation of debris particles, then the second pulling element can move further by a compression of the elastic element. 
         [0017]    Preferably, the elastic element is embodied or formed as a wave spring washer or other elastomeric body. The elastomeric body can, for example, be embodied or formed as a ring. A uniform resistance to a compression thus results around the pulling device, so that the risk of the pulling device being deformed transversally to the pulling direction is relatively low. 
         [0018]    Preferably, the first pulling element includes a first step with a first surface directed perpendicular to the pulling direction and the second pulling element comprises a second step with a second surface directed perpendicular to the pulling direction, wherein the elastic element loads the first surface and the second surfaces against one another. The term “perpendicular” is not to be understood in the mathematically exact sense here. The two surfaces merely need to be capable of transferring a force in the pulling direction. The pulling device thus always has its maximum length during a movement in the pulling direction. During a movement in the reset direction, however, the elastic element can be compressed so that the length of the pulling device can be decreased. 
         [0019]    Alternatively or additionally, the housing includes a first housing part and a second housing part. The first housing part can be displaced relative to the second housing part in the reset direction. With this embodiment, the length of the housing can be extended so that even if fouling is present between the pulling device and the interior of the housing, expressed more accurately, an inner front face of the housing, damage to the housing or the pulling device can be prevented in that the first housing part is displaced relative to the second housing part and the length of the housing is thus increased. 
         [0020]    Here, it is provided that one of the two housing parts has a marking that is visible when the second length is present and not visible when the first length is present. The two housing parts are arranged so that they telescope into one another. Expediently, the marking is then affixed to the housing part that is inserted into the other housing part. 
         [0021]    Preferably, the first housing part and the second housing part are engaged via a locking connection. The locking connection engages when the first housing part is slid into the second housing part, so that the housing then has its “target length.” At this target length, blind rivet fasteners can be set. If, during a reset movement of the pulling device, the situation occurs in which the pulling device will collide with the housing, for example, due to a defect in a sensor, faulty programming or an accumulation of debris, then the first housing part is slid out of the second housing part after a force necessary to release the locking connection is overcome. 
         [0022]    Preferably, the locking connection includes at least one spring element that is connected to one of the housing parts and engaged with the other of the housing parts in a non-positive fit. The spring element can, for example, engage in a groove. To release the locking connection, a force must be applied which presses the spring element out of the groove. 
         [0023]    Here, it is preferred that the spring element is embodied or formed as a spring clip. A spring clip is a relatively simply designed constructional element which can easily be used to produce a locking connection. 
         [0024]    Embodiments of the invention are directed to a blind rivet setting device that includes a housing, a pulling device that is at least partially arranged in the housing and a drive that acts on the pulling device in a pulling direction and in a reset direction oriented opposite to the pulling direction. A length of at least one of the housing and the pulling device is changeable from a first length to a second length when a predetermined force is exceeded. 
         [0025]    According to embodiments, the pulling device can include a chuck housing and clamping jaws loaded into the chuck housing by a compression spring. The housing may include a nose piece and, in a resting state, the clamping jaws are displaceable into an opened position by the nose piece when the length is the first length and are not displaceable into the opened position when the length is the second length. 
         [0026]    In accordance with other embodiments, a difference between the first length and the second length can lie within the range of 1 to 5 mm. 
         [0027]    According to still other embodiments, the pulling device may include a first pulling element, a second pulling element and an elastic element that can be structured and arranged so that, when the pulling device is acted on in a pulling direction, the first pulling element and the second pulling element are positively engaged and, when the pulling device is acted on in the reset direction, the elastic element acts between the first pulling element and the second pulling element. The elastic element may include one of a wave spring washer or other elastomeric body. The first pulling element may include a first step with a first surface directed crosswise to the pulling direction and the second pulling element can include a second step with a second surface directed crosswise to the pulling direction, and the elastic element may be arranged to load the first surface and the second surface against one another. 
         [0028]    In embodiments, the housing can include a first housing part and a second housing part that can be structured and arranged so that, in the reset direction, the first housing part can be displaced relative to the second housing part. One of the first and second housing parts may include a marking that is visible when the second length is present and not visible when the first length is present. The first housing part and the second housing part may be engageable via a locking connection. The locking connection can include at least one spring element that may be connected to one of the first and second housing parts and engaged with the other of the first and second housing parts in a non-positive fit. 
         [0029]    According to still other embodiments, the spring element may include a spring clip. 
         [0030]    Embodiments of the invention are directed to a method of operating the above-described blind rivet setting device. The method includes pulling the pulling device in the driving direction to move the chuck from an initial position to a position away from a front face of the housing, moving the pulling device in the reset direction to move the chuck toward the initial position, and, when debris in the housing prevents the chuck from returning to the initial position, changing a length of at least one of the pulling device and housing. 
         [0031]    According to embodiments, the pulling device can include a first pulling element and a second pulling element that may be structured and arranged so that, in the driving direction, the first pulling element is engaged with the second pulling device so that the pulling device has the first length, and in the reset direction, the debris causes the first pulling element to be displaced from the second pulling element so that the pulling device has the second length. The second length can be shorter than the first length. The pulling device may further include an elastic element arranged to return the pulling device to the first length when the debris is removed. 
         [0032]    In accordance with still yet other embodiments of the present invention, the housing may include a first housing part and a second housing part that can be structured and arranged so that, in the driving direction, the housing has the first length, and in the reset direction, the debris causes the first housing part to be displaceable relative to the second housing part so that the housing has the second length. The second length can be longer than the first length. The housing may further include an adjustable connection between the first housing part and the second housing part. The method can also include viewing a marking on the housing to confirm that the housing has the second length. 
         [0033]    Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein: 
           [0035]      FIG. 1  shows a first embodiment of a blind rivet setting device in a partial view; 
           [0036]      FIG. 2  shows a section D-D through a part of the blind rivet setting device according to  FIG. 3 ; 
           [0037]      FIG. 3  shows a side view of a part of a blind rivet setting device; 
           [0038]      FIG. 4  shows a section E-E according to  FIG. 2 ; 
           [0039]      FIG. 5  shows a part of the blind rivet setting device in a perspective representation; and 
           [0040]      FIG. 6  shows the part of the blind rivet setting device in an exploded view. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0041]    The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied or formed in practice. 
         [0042]      FIG. 1  shows a part of a blind rivet setting device  1  with a housing  2  that is embodied or formed as a steel sleeve in the region shown here. The housing  2  comprises a front face  3 , into which a nose piece  4  is screwed. The nose piece  4  comprises a centric opening  5 , through which a pulling mandrel of a blind rivet fastener can be inserted into the housing  2 . 
         [0043]    In the housing  2 , a pulling device is arranged which comprises a first pulling element  6  and a second pulling element  7 . The second pulling element  7  is connected to a drive device  8  via a counterpart  24 . In this exemplary embodiment, drive device  8  includes a threaded spindle. In a manner known per se, the threaded spindle is connected to a threaded nut or a ball screw nut, which can be driven by an electric, pneumatic or hydraulic drive. 
         [0044]    The first pulling element  6  acts on a chuck housing  9 . In the chuck housing  9 , multiple clamping jaws  10  are arranged which are loaded into the chuck housing  9  by a compression spring  11 . Between the compression spring  11  and the clamping jaws  10 , a spacer sleeve  12  can be provided. 
         [0045]    The chuck housing  9  comprises support surfaces  13  that are sloped to a center axis  14 . The clamping jaws  10  bear against the support surfaces  13 . 
         [0046]    The chuck housing  9  can be moved in a pulling direction  15  via the two pulling elements  6 ,  7 , the counterpart  24  and the drive device  8  in order to set a blind rivet fastener, that is, to form a closing head on the blind rivet fastener. The chuck housing  9  can also be moved in a reset direction  16  when the setting operation is complete in order to once again assume the initial position illustrated in  FIG. 1 . 
         [0047]    In the initial position illustrated in  FIG. 1 , the chuck housing  9  has been displaced a relatively far distance towards the front face  3  of the housing  2  so that the clamping jaws  10  come to bear against the nose piece  4 . The clamping jaws  10  are moved slightly in the direction of the compression spring  11  by the nose piece  4  against the force of the compression spring  11 , so that the clamping jaws can move radially outwards along the support surfaces  13 . As a result, an accommodation space  17  between the clamping jaws  10  is expanded so that a pulling mandrel of a blind rivet fastener can be easily inserted or removed. 
         [0048]    If, however, the drive device  8  moves the chuck housing  9  in the pulling direction  15 , then the clamping jaws  10  move clear of the nose piece  4  and are moved radially inwards on the support surfaces  13  by the compression spring  11 , so that they can grip the pulling mandrel. For this purpose, the clamping jaws  10  comprise on the radial inside thereof a surface geometry  18  which improves an engagement between the clamping jaws  10  and the pulling mandrel, e.g., teeth, fluting or the like. 
         [0049]    If the setting operation is complete, then the drive device  8  once again moves the chuck housing  9  in the direction of the front face  3 , so that the clamping jaws  10  open, that is, are displaced into an opened position, and release the pulling mandrel. 
         [0050]    The first pulling element  6  is engaged with the second pulling element  7  in a positive fit in the pulling direction. For this purpose, the first pulling element  6  comprises a first step  19 , which in the present case points radially inwards and has a first surface  20  directed roughly perpendicular to the center axis  14 . In a similar manner, the second pulling element  7  comprises a step  21  which is directed radially inwards and has a second surface  22  that is likewise directed roughly perpendicular to the center axis  14 . The term “perpendicular” is not to be understood in the mathematically narrow sense here. When the two surfaces  20 ,  22  bear against one another, they must still be capable of transferring a force in the pulling direction  15 . 
         [0051]    An elastic element  23 , preferably a wave spring washer, annularly surrounds the second pulling element  7 . The elastic element  23  is arranged between the first step  19  of the first pulling element  6  and the counterpart  24  which is screwed onto the second pulling element  7  or connected to the second pulling element  7  in a different manner. The elastic element  23  is arranged prestressed between the counterpart  24  and the first step  19  without play, so that the first step  19  bears with its first surface  20  against the second surface  22  of the second step  21  without play. The counterpart  24  is illustrated here as an individual element. However, it is to be readily understood that counterpart  24  can also be embodied or formed in one piece with the second pulling element  7  or the drive device  8 , or it could be composed of multiple parts. 
         [0052]    If the drive device  8  and therefore the counterpart  24  are moved in the pulling direction  15 , then the second pulling element  7  pulls the first pulling element  6  along in the pulling direction  15  via the surface pairing of the two surfaces  20 ,  22  and thus moves the chuck housing  9  away from the front face  3  of the housing  2 . In this manner, a setting operation for a blind rivet fastener is performed. 
         [0053]    After the setting operation, the chuck housing  9  is once again moved back into its initial position. Here, the movement is transferred from the drive device  8  to the first pulling element  6  via the elastic element  23 . 
         [0054]    However, should debris have accumulated in an intermediate space  25  between the chuck housing  9  and the front face  3  of the housing  2 , which debris prevents a movement of the chuck housing  9  into the initial position illustrated in  FIG. 1 , then the second pulling element  7  can indeed be moved all the way into the initial position illustrated in  FIG. 1 . However, the movement of the chuck housing  9  can be stopped earlier, since the first pulling element  6  can come away from the second pulling element  7 , expressed more accurately, the first step  19  can come away from the second step  21 . In this case, the elastic element  23  is compressed. The elastic element  23  thus relieves forces which could otherwise destroy the housing  2 . 
         [0055]    If the chuck housing  9  can no longer be moved far enough towards the nose piece  4 , then the clamping jaws  10  are no longer sufficiently opened. The user of the blind rivet setting device notices this in that a pulling mandrel of a blind rivet fastener can be inserted into the clamping jaws  10  only with difficulty or not at all, or in that it becomes correspondingly difficult to pull a pulling mandrel out of the housing  2 . The user can then partially disassemble the housing in order to expose the intermediate space  25  and, e.g., remove the debris located there. 
         [0056]    Since the elastic element  23  can be compressed, the length of the pulling device is variable. If the two surfaces  20 ,  22  bear against one another, then the pulling device has a first length. If the two steps  19 ,  21  are moved relative to one another so that the two surfaces  20 ,  22  distance themselves from one another and the elastic element  23  is compressed, then the pulling device has a second length that is shorter than the first length. Only when the pulling device has the first length are the clamping jaws  10  sufficiently opened by the nose piece  4 . 
         [0057]    The compression of the elastic element  23 , and therefore the change in length, can be small. It lies within a range of, e.g., 1 to 5 mm. 
         [0058]    An additional solution that can also be used together with the solution illustrated in  FIG. 1  is shown in  FIGS. 2 through 6 . Identical and corresponding elements are provided with the same reference numerals. 
         [0059]    The pulling device  26  is in this case only shown from the outside. 
         [0060]    The housing comprises a first housing part  2   a  and a second housing part  2   b.  The first housing part  2   a  is inserted into the second housing part  2   b  in a telescoping manner. A spring element  27  in the form of a spring clip bent in a U shape is connected to the second housing part  2   b,  for example, in that it is inserted into a recess  28  that is embodied or formed in a corresponding U-shape. The spring element  27  engages in a first circumferential groove  29  embodied or formed on the second housing part  2   a  when the blind rivet setting device  1  is ready for operation. In this case, with the two housing parts  2   a,    2   b,  the housing has a first length. 
         [0061]    If a problem should occur during the reset movement of the pulling device  26 , e.g., due to an accumulation of debris in the intermediate space  25 , then the first housing part  2   a  is slid out of the second housing part  2   b  in the reset direction  16  by the pulling device  26 . For this purpose, the spring clip  27  must be pushed radially outwards out of the first circumferential groove  29 , for which a certain force is necessary. This force is larger than the force of the compression spring  11 . On the first housing part  2   a,  a second circumferential groove  31  can be provided, into which the spring element  27  engages again once the first housing part  2   a  has been slightly slid out of the second housing part  2   b.  Between the two circumferential grooves  29 ,  31 , a marking  30  can be provided which indicates to a user that the second housing part  2   b  has moved relative to the first housing part  2   a.  The marking thus shows the user that maintenance is necessary. 
         [0062]    The spring element  27  forms a locking connection with the first circumferential groove  29 , since a transverse clip of the spring element  27  can engage in the first circumferential groove  29  when the first housing part  2   a  is slid far enough into the second housing part  2   b.  A certain force is also necessary for this. 
         [0063]    In a manner not illustrated in greater detail, the spring element can also be embodied or formed as a spring clip that is inserted into the second housing part  2   b  in a radial direction and subsequently engages in a corresponding circumferential groove  29  on the first housing part  2   a.    
         [0064]    It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.