Patent Publication Number: US-2023158645-A1

Title: Torque wrench as power wrench

Description:
The invention relates to a torque wrench as a power wrench according to the preamble of claim  1 . 
     Torque wrenches, so-called power wrenches, are hand-held bolting devices for large bolting connections. Such torque wrenches are generally known in various designs for torque ranges between approx. 150 Nm and 10000 Nm. 
     In principle, such torque wrenches have a multi-stage design: a relatively highspeed drive motor, for example an electric motor, and a downstream intermediate gearbox are arranged in series in a housing with at least one handle. In addition, known torque wrenches are usually designed as so-called shut-off wrenches, which switch off automatically after being switched on when a presettable bolting torque is reached. The necessary actuation, display and control elements are contained in the housing serving as motor and electronics housing. Downstream of the intermediate gearbox and adjacent to the housing is a heavy, stable bolting gearbox in the form of a planetary gearbox for the high torques required in a bolting operation. The planetary gear has an outer ring gear to which, in particular in contrast to a simple hand drill, a radially projecting torque support foot is attached. During a screwing/bolting operation, this torque support foot pivots against a fixed support point required in the vicinity of the bolting operation and supports there the high reaction forces occurring at the planetary gear, which could no longer be supported by hand by an operator. 
     In the case of a rotationally fixed connection between the housing and the planetary gear, the ring gear would swivel together with the torque support foot and the hand-guided housing during a bolting process until the torque support foot would rest against its fixed support point. This would create the risk that, in tight spaces and with the large torques that occur during a bolting operation, the housing and/or parts of an operator’s body could be swiveled with great force against an obstacle and jammed. For safety reasons and to protect operators, the rotary motion of the outer sun gear of the bolt drive is therefore decoupled from the rotary motion of the hand-guided housing, for example by the ring gear of the planetary gear being rotatably mounted in an end ring part of the housing that partially overlaps the ring gear. 
     In known torque wrenches, the drive motor, in particular an electric motor, and the downstream intermediate gearbox are arranged in the housing so that they cannot rotate. In typical arrangements, motor output torques of approx. 1 Nm occur during a tightening operation. With the intermediate gearbox downstream of the drive motor, which is held in the housing so that it cannot rotate, the output speed of the drive motor is reduced by a predetermined reduction ratio with a correspondingly increased intermediate gearbox output torque. Typically, a reduction ratio of about 10:1 is selected with a corresponding 10-fold output torque of about 10 Nm. Due to the rotatable connection between the hand-guided housing and the heavy bolting gearbox in the form of a planetary gearbox explained above, in this previous arrangement only the reaction forces occurring at the planetary gearbox are supported by the torque support foot, while the intermediate gearbox output torque must be supported by an operator by hand. 
     The above-mentioned typical intermediate gearbox output torques of approx. 10 Nm, which have to be supported by an operator as reaction forces, require a great deal of effort, which makes working with a torque wrench over a long period of time strenuous and arduous. In addition, designs and dimensioning with higher intermediate gearbox output torques are not possible and are limited by the robustness of operators. 
     It is an object of the invention to develop a torque wrench in the form of a power wrench in such a way that the reaction forces occurring on a hand-guided housing during a bolting operation, which have to be supported by an operator, are reduced. 
     This object is solved by means of the features of claim  1 . Advantageous embodiments are part of the subclaims referring back thereto. 
     According to claim  1 , a torque wrench is provided in the form of a power wrench having a drive motor with a predetermined, preferably high, speed and predetermined motor output torque. Furthermore, an intermediate gearbox is provided downstream of the drive motor, which reduces the output speed of the drive motor with a predetermined reduction ratio, preferably at a correspondingly increased intermediate gearbox output torque. In addition, a bolting gearbox is provided downstream of the intermediate gearbox with a bolting tool part on the output side, the bolting gearbox reducing the output speed of the intermediate gearbox with a predetermined reduction ratio, preferably at a correspondingly increased bolting gearbox output torque which is required for a specific bolting operation. Furthermore, a housing with at least one handle is provided, in which the drive motor and the intermediate gearbox are arranged in sequence, it being preferably provided that the housing is to be held by an operator at the at least one handle during a bolting operation and/or reaction forces occurring at the housing are to be supported as rotational forces. The bolting gearbox is a planetary gearbox with an outer ring gear with internal toothing, the ring gear being rotatably mounted on the housing and having a radially projecting torque support foot which, during a bolting operation, pivots against a required fixed support point and supports there the reaction forces occurring on the planetary gearbox. 
     According to the invention, the drive motor is non-rotatably arranged and fixed in the housing, and the intermediate gearbox is rotatably mounted in the housing and is non-rotatably connected to the ring gear. As a result, only the reaction forces occurring on the housing due to the drive motor need to be supported by an operator during a screwing/bolting process and/or the reaction forces occurring due to the intermediate gearbox are additionally supported with the torque support foot during a bolting process. 
     In other words, in the arrangement according to the invention, too, the drive motor is non-rotatably arranged and fixed in the housing. However, the intermediate gear box is mounted rotatably in the housing and is connected non-rotatably to the ring gear of the planetary gear box. During a screwing/bolting process, only the reaction forces occurring at the housing due to the drive motor occur, which, as explained above, can typically be dimensioned in the order of 1 Nm and are to be supported by an operator. The higher reaction forces occurring due to the intermediate gear box are additionally supported by the torque support foot due to the non-rotatable connection with the ring gear. 
     With the arrangement according to the invention, the reaction forces occurring at the housing can be greatly reduced for effort-saving and convenient handling compared to the state of the art and/or clearances for dimensioning with higher intermediate gear box output torques become possible, since, if necessary, relatively low output torques of the drive motor can still be well supported by hand. 
     In principle, the arrangement according to the invention is possible with different motors, in particular with electric motors, although pneumatic motors or hydraulic motors can also be used if necessary. 
     In one specific embodiment, a handle can be arranged on the housing as a pistol grip. In an embodiment as a cordless wrench with an electric motor, a receptacle for an energy storage device, for example a rechargeable battery, for supplying energy to the electric motor can be attached to the pistol grip. 
     The torque support foot can be designed to be removable, whereby an external toothing is attached to the ring gear in a partial area of it, onto which a connection ring of the torque support foot with associated internal toothing can be attached and fixed. 
     Furthermore, the output of the planetary gear box can be designed as an output polygon, for example as an output square, onto which an exchangeable socket can be fitted as a bolting tool part. 
     A simple design according to the invention results when the output rotary shafts of the drive motor, the intermediate gearbox and the planetary gearbox are concentrically aligned and the inner area of the housing is cylindrical in its basic shape. In principle, however, angular arrangements are also possible. 
     In a particularly preferred concrete arrangement, the rotatable mounting of the intermediate gear box in the housing is implemented in such a way that, on the one hand, an adapter ring is rotatably mounted on a shaft section between the drive motor and the intermediate gearbox, to which an adjacent region of the intermediate gearbox, in particular an intermediate gearbox housing region overlapping the adapter ring, is rotatably connected. On the other hand, a toothed disc is arranged concentrically on an opposite region of the intermediate gearbox, in particular an intermediate gearbox housing region, if necessary via a driver ring, and is non-rotatably connected, which toothed disc engages with its external toothing in the internal toothing of the ring gear. This ensures on the one hand the rotatability of the intermediate gearbox in the housing and on the other hand the non-rotatable connection with the ring gear. The planetary gearbox can be plugged together with the housing and mounted as a separate component. An output pinion of the intermediate gearbox is guided through a central opening in the toothed pulley and engages in the planetary gearbox, where it meshes in particular with a planetary gear. 
     The reduction ratio of the intermediate gearbox is preferably of the order of 1:10. Alternatively or additionally, it is provided that the motor output torque is of the order of 1 Nm and the intermediate gearbox output torque is of the order of 10 Nm. 
     The arrangement according to the invention can advantageously be used in conjunction with a wrench design in the form of a shut-off wrench, which automatically switches off when a presettable bolting torque is reached. 
     Furthermore, a method is also claimed. The advantages achievable with the method according to the invention are identical to those of the torque wrench according to the invention, so that reference is made to the explanations previously given in order to avoid repetition. 
    
    
     
       With the aid of a drawing, embodiments of the invention are further explained merely by way of example. 
       It shows: 
         FIG.  1    a perspective view of a torque wrench as a power wrench with a torque support foot, 
         FIG.  2    a side view of a similar torque wrench without a support foot, 
         FIG.  3    a schematic longitudinal section through a housing and a part of a bolting gearbox, and 
         FIG.  4    a top view onto a sun gear of the bolting gearbox. 
     
    
    
     In  FIG.  1   , a torque wrench  1  is shown as a cordless bolt wrench with a housing  2 , with a handle  3  as a pistol grip, to the end of which is attached a receptacle  4  for a battery, for example, as an energy storage device for supplying energy to an electric motor  13  arranged in the housing  2  as a drive motor. 
     A bolting gearbox  5  with an outer sun gear  6  is rotatably connected to the housing  2 , to which a torque support foot  7  is attached in a non-rotatable manner. As shown in  FIG.  2   , an external toothing  8  is attached to a section of the sun gear  6 , onto which the torque support foot  7  can be fitted and fixed with an associated internal toothing. 
       FIG.  2    also shows that the output of the bolting gearbox  5  is designed as an output polygon, here exemplarily as an output square  9 , onto which an exchangeable socket  10  can be plugged as a bolting tool part. 
     As can be seen from  FIG.  2    in conjunction with the longitudinal section shown in  FIG.  3   , the housing  2  is made up of several parts and consists in particular of a stable housing inner part  11  onto which shell parts  12  are fitted and fixed to form the handle  3  and to accommodate switching, control and display elements. 
     In the housing inner part  11  of relevance for the invention according to  FIG.  3   , further generally referred to as housing  2 , an electric motor  13 , preferably rotating relatively quickly, with a rotary shaft  14  is arranged and shown schematically. During a bolting operation, with the design adopted here, torques in the order of approximately 1 Nm, for example, occur at the rotary shaft, in particular at an output-side shaft section  15 . 
     The electric motor  13  is followed by a schematically shown intermediate gearbox  16 , which here reduces the speed of the electric motor  13  with a reduction ratio of 10:1, whereby an intermediate gearbox output torque of approximately 10 Nm occurs at an output pinion  17  of the intermediate gearbox  16 . 
     The intermediate gearbox  16  has an intermediate gearbox housing section  18  projecting towards the electric motor  13 , which is connected to an adapter ring  19  in a non-rotatable manner. The adapter ring  19  is rotatably mounted on the shaft section  15  of the rotary shaft  14  by means of a ball bearing  20 . 
     At the opposite end of the intermediate gearbox  16 , a driver ring  21  is non-rotatably connected to the intermediate gearbox housing, to which in turn a toothed disc  22  is attached at the end. The external toothing of the toothed disk  22  engage in the internal toothing  23  of a ring gear  24  of the bolting gearbox  5  in the form of a planetary gearbox. One section of the ring gear  24  is rotatably inserted into a receiving ring part  25  at the end of the housing  2 . The further structure of the bolting gearbox  5  is not relevant according to the invention and is therefore not shown further. Only in the upper area of the ring gear  24  is schematically shown a part of a planetary gear carrier  26  with a planetary gear  27 , in which the output pinion  17  engages. 
     The thick dashed line  28  and the rotary arrows  29  and  30  are intended to illustrate that the intermediate gearbox  16  is rotatably arranged in the housing  2  and has a non-rotatable connection to the bolting gearbox  5  or the ring gear  24  and thus to the torque support foot  7 , whereby the intermediate gearbox output torque is also supported by the torque support foot  7 . During a bolting process, only the comparatively small motor output torque is applied to the housing  2  as a reaction force, which must be supported by an operator as a reaction force. 
       FIG.  4    shows a top view of the ring gear  24  with its internal toothing  23 , and 
       FIG.  5    shows a corresponding longitudinal section. As shown, the external toothing of the toothed disk  22  engage in the internal toothing  23  for a non-rotatable connection with the intermediate gearbox  16 . 
     
       
         
           
               
               
             
               
                 List of reference signs 
               
             
            
               
                 
                   1 
                 
                 torque wrench 
               
               
                 
                   2 
                 
                 housing 
               
               
                 
                   3 
                 
                 handle 
               
               
                 
                   4 
                 
                 receptacle 
               
               
                 
                   5 
                 
                 bolting gearbox 
               
               
                 
                   6 
                 
                 sun gear 
               
               
                 
                   7 
                 
                 torque support foot 
               
               
                 
                   8 
                 
                 outer toothing 
               
               
                 
                   9 
                 
                 drive square 
               
               
                 
                   10 
                 
                 socket 
               
               
                 
                   11 
                 
                 internal part of the housing 
               
               
                 
                   12 
                 
                 shell parts 
               
               
                 
                   13 
                 
                 electric motor 
               
               
                 
                   14 
                 
                 rotary shaft 
               
               
                 
                   15 
                 
                 shaft section 
               
               
                 
                   16 
                 
                 intermediate gearbox 
               
               
                 
                   17 
                 
                 output pinion 
               
               
                 
                   18 
                 
                 intermediate gearbox housing area 
               
               
                 
                   19 
                 
                 adapter ring 
               
               
                 
                   20 
                 
                 ball bearing 
               
               
                 
                   21 
                 
                 driver ring 
               
               
                 
                   22 
                 
                 toothed disc 
               
               
                 
                   23 
                 
                 internal thoothing 
               
               
                 
                   24 
                 
                 ring gear 
               
               
                 
                   25 
                 
                 receiving ring part 
               
               
                 
                   26 
                 
                 planet gear carrier 
               
               
                 
                   27 
                 
                 planetary gear 
               
               
                 
                   28 
                 
                 line 
               
               
                 
                   29 
                 
                 rotary arrow 
               
               
                 
                   30 
                 
                 rotary arrow