Patent Publication Number: US-8991779-B2

Title: Power tool holder

Description:
FIELD OF THE INVENTION 
     The invention relates to a power tool holder according to the preamble of claim  1 . 
     BACKGROUND ART 
     A power tool holder is depicted in  FIG. 1 , indicated with reference numeral  1 . Such holders  1  are previously known and may be used to fasten a power tool  6  to a support arm  9 , which may be telescopic. The purpose of the combination of the arm  9  and the holder  1  is to relieve a worker from the weight and torque reaction forces from the tool when using the tool, for instance in nut running or drilling with the tool. In  FIG. 1 , the known holder holding an angled power tool  6  is shown. The tool head is angled at 90° to the body of the tool.  FIG. 2  depicts a known holder holding a straight power tool. 
     Such conventional power tool holders are by themselves quite uncomplicated devices, normally comprising two clamping parts that are held together by some means that can be used to force them together when clamping the power tool. 
     Since the force and torque that can be exerted by the power tool may be quite high, depending on the tool used, it is important that the tool is tightly fastened in the tool holder. Should the tool move in the tool holder during use, it may be detrimental to the precision with which the tool can work, for instance the amount of torque that controllably can be delivered to a screw joint. Also, the material of the tool housing in the connection region between tool and the holder may be damaged by such movements. 
     The importance of a firm connection between the tool and the holder is reflected in the propensity of workers to overtighten the holder when attaching it to the tool. This overtightening may in itself lead to deformation of the housing of the tool, thus damaging vital internal parts such as the gears, motor or torque transmitter. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to propose a solution for or a reduction of the problems of prior art. A main object is consequently to reduce the risk of damaging a power tool when tightly attaching it to a power tool holder. 
     The invention provides a solution with a power tool holder having the features of claim  1 . 
     By providing at least one clamping part comprising at least one through hole located adjacent to the clamping surface of said clamping part, the clamping surface will flex when under pressure clamping a power tool. This flexing translates into a larger contact surface between the clamping part and the power tool and thus the surface pressure on the power tool is decreased compared to a prior art holder clamped with the same tension in the connection part. This considerably lessens the risk of damaging the power tool when tightening the holder. 
     Further advantageous aspects of the invention are disclosed in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Advantageous embodiments of the invention are described below in detail with reference to the accompanying drawings. On the drawings: 
         FIG. 1  illustrates a power tool holder according to prior art connected to an angled power tool, 
         FIG. 2  illustrates a power tool holder according to prior art connected to a straight power tool, 
         FIG. 3  illustrates a power tool holder according to the invention, and 
         FIG. 4  illustrates another power tool holder according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 3  illustrates as an example a power tool holder  1  comprising at least two clamping parts  20 ,  21  mutually movably connected to each other by at least one adjustable connection part  3 . In  FIG. 3 , two connection parts  3  in the form of screws are shown as an example. In the figure, the clamping part  21  is provided with a hole (not shown explicitly) through which the screw  3  runs and the clamping part  20  is provided with a hole (not shown explicitly) with a thread in which the screw fits. In this way, by tightening of the screw, the clamping parts  20 ,  21  may be driven towards each other, clamping the tool  6  in between. 
     In  FIG. 3  there are two connection parts, but only one may be enough. A holder according to the one in  FIG. 3  with only one connection part would mean that the two connection parts would be swivellingly movable in relation to each other. This swivelling would be counteracted when the two clamping parts are close to the tool during clamping, since the tool then gets in the way preventing the swivelling. To further prevent swivelling, the single connection part could additionally comprise a control part that interconnects with a portion of each of the clamping parts. Such a control part could be a piece of material including grooves that mates with corresponding rims on the clamping parts, or vice versa, allowing mutual sliding but preventing mutual rotation of the clamping parts. Other connection parts  3  are also conceivable, as long they provide for an adjustable connection of the clamping parts. Also, the number of connection parts may also be more than one or two, for instance three or more, depending on the particular implementation. 
     As, seen in  FIG. 3 , there are at least two clamping parts  20 ,  21 . They have each a clamping surface  20   a ,  21   a , which clamping surfaces  20   a ,  21   a  are facing each other. In the figure, the clamping surfaces are provided in the form of an arc-like shape comprising two flat portions at an angle to each other. Between the surfaces  20   a ,  21   a , a clamping space  5  is formed, i.e. the room  5  between the clamping parts that will accommodate the power tool  6 . The power tool  6  can be clamped by an adjustment of the connection part  3  to move the clamping parts  20 ,  21  together, for instance by rotation of screws as mentioned above. 
     A distinguishing feature of the holder  1  of the invention is that at least one clamping part  20 ,  21  comprises at least one through hole  7  located adjacent to the clamping surface  20   a ,  21   a  of said clamping part  20 ,  21  such that the clamping surface  20   a ,  21   a  will flex when under pressure clamping a power tool  6 . This flexing is due to the relatively thin wall  10  of material, between the hole  7  and the clamping surface, that will yield somewhat when under pressure. The flexing of the clamping surface provides a larger contact surface between the clamping part  20 ,  21  and the power tool  6  leading to a lower surface pressure on the tool  6  for a given clamping tension in the connection part(s). At least one through hole  7 , as mentioned earlier, is needed in order to provide this benefit. However more holes may also be provided, as is the case in  FIG. 3 . It should be noted that even though the surface pressure on the power tool will be lower, the frictional force between the power tool and the holder stays the same for a given tension in the connection part(s) since the contact surface between the tool and the holder has increased due to the flexing of the clamping surface(s). 
     Thus, instead of making contact substantially along a line formed by the points of contact between the power tool and the holder as in the prior art, the contact surface according to the holder of the invention will be in the form of a surface due to the flexing of the clamping surfaces of the invention. 
     As mentioned, the power tool holder  1  according to the invention may comprise at least one clamping surface  20   a ,  21  that comprises two flat portions. Such portions may be directed towards the clamping space  5  at an angle of less than 180° between them, as seen in  FIG. 3 . This makes it possible to use the power tool holder with power tools of different diameters; each such different tool will make contact with the two flat portions of the clamping surface at slightly different positions. Thus, a universal clamping character of the tool holder is afforded. 
     A particular case of the power tool holder  1  according to the invention would be a tool holder where each clamping surface  20   a ,  21   a  of two clamping parts  20 ,  21  comprises two flat portions directed towards the clamping space  5  at an angle of less than 180° between them. This resembles the case of  FIGS. 3 and 4  and constitutes a stable solution that firmly will clamp a tool. 
     It should be noted that other peripheries of the clamping surfaces, even convex ones, given the right flex of the surface are possible. 
     As has been mentioned, at least one through hole  7  should be provided in at least one clamping part of the tool holder. A power tool holder  1  according to any of the embodiments of the invention wherein each clamping part  20 ,  21  comprises at least one such through hole  7  would provide the benefit of further reducing surface pressure on a tool when clamped with a given tension in the connection part(s). Also, since all clamping parts in this case have a clamping surface that flexes, the overall distribution of surface pressure on a clamped tool will be more even. The through holes would be located adjacent to the clamping surface  20   a ,  21   a  of said each clamping part  20 ,  21 . 
     A variant of the previous embodiment would be a power tool holder wherein each clamping part  20 ,  21  comprises one through hole  7 . Such an embodiment is depicted as an example in  FIG. 4 . Having only one hole potentially means less machining steps when producing the power tool holder, so production cost may be lower. 
     In any of the embodiments of the power tool holder  1  according the invention, a through hole  7  may have a cross section form of an elongated oval. This form of the hole has been depicted as an example in  FIGS. 3 and 4  and has the advantage of providing a good flexibility along the clamping surface. In this way, power tools having different diameters that engage with different portions of the clamping surface could be accommodated. 
     The power tool holder  1  according to any of the previous embodiments may in one embodiment comprise two adjustment parts  3  interconnecting the clamping parts  20 ,  21 . This is a straightforward solution that provides a balanced pressure when clamping a power tool. It has been shown as an example in the  FIGS. 3 and 4 . 
     A suitable material for a clamping part  20 ,  21  comprising at least one through hole  7  is high-tensile steel having a yield strength between around 750-1500 MPa, for instance about 900-1100 MPa. This choice of material provides good flexibility with moderate material use and such material also does not suffer from material fatigue. Of course, other materials may also be used, such as other metals or synthetic materials. 
     A through hole  7  in a clamping part may be filled with a material which is softer than the material of the clamping part, preferably a highly flexible material in order not to impair the flexing ability of the clamping surface. Filling a hole with such a material would for instance prevent the hole from getting caught on some protruding object when moving the power tool holder about. 
     The invention also comprises an assembly comprising a power tool holder  1  according to any of the previous embodiments and a support arm  9 . The assembly may further comprise a power tool  6 .