Abstract:
A device for locking, an electrical device to an accessory part has a guide configured to guide the accessory part in a predetermined movement direction as it moves between a locking position in which it is locked the electrical device and a removal position in which it is removed from the electrical device, the guide having a break in at least one location between the locking position and removal position, and at the location a force acting on the accessory part moves the accessory part into a safety position in which the accessory part is prevented from moving further along the guide into the removal position.

Description:
CROSS-REFERENCE 
     The invention described and claimed hereinbelow is also described in DE 102004044331.9, filed Sep. 9, 2004. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a device for locking an electrical device to an accessory part. 
     Locking devices of this type are used, for example, to reliably connect cordless hand-guided power tools to a battery pack used as a power supply. 
     The known locking devices usually have a linear guide provided on the power tool into which the battery pack is slid until, after being slid all the way in, it comes into contact with a stop and is locked in this position in relation to the power tool, while simultaneously producing an electrical connection between a battery of the battery pack and an electrical circuit of a consumer of the power tool. The locking usually occurs with the aid of a latch, which is supported in a housing of the power tool so that it can move in opposition to the force of a spring and which the spring force brings into engagement with a detent recess in the battery pack. A release mechanism is used to release the connection and usually has a push button, which is situated in the region of the guide and is manually actuated in order to disengage the latch from the detent recess and release the battery pack. The battery pack is then slid along the guide into a removal position in which it no longer engages the electrical device. 
     Since the movement resistance while the battery pack is being slid into the guide of the power tool generally increases toward the end of the insertion path due to the increasing size of the friction surfaces and due to the contact between the electrical terminals, the user can be given the impression that the two components are properly locked in position although this is not yet the case. This can result in the battery pack slipping out of the guide during transport or operation of the power tool when the latter is tilted downward toward the removal position, which can lead to property damage or injury. 
     In order to prevent the battery pack from unintentionally detaching from the power tool, some of the applicant&#39;s larger and heavier power tools are already provided with a two-stage locking device called a double locking mechanism in which, as the battery pack is slid into the guide, the spring force of a spring-loaded latch brings it into engagement with two detent recesses provided in the battery pack, one after the other in the insertion direction. When the latch engages with the first detent recess, the battery pack is only secured in relation to the power tool, whereas an electrical connection is only produced when the latch engages in the second detent recess. 
     This does make it possible to prevent the battery pack from unintentionally detaching from the power tool when the latch is not engaging in the second detent recess or is not properly engaging in it, for example because the user has not slid the battery pack all the way into the locking position in the guide. But if the user does not hold the battery pack while actuating the release mechanism and the guide is simultaneously pointing obliquely downward from the locking position, then even a two-stage locking mechanism is unable to reliably prevent the battery pack from falling out. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a device for locking an electrical device to an accessory part, which avoids the disadvantages of the prior art. 
     In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a device for locking, an electrical device to an accessory part, comprising a guide configured to guide the accessory part in a predetermined movement direction as it moves between a locking position in which it is locked the electrical device and a removal position in which it is removed from the electrical device, said guide having a break in at least one location between the locking position and removal position, and at said location a force acting on the accessory part moves the accessory part into a safety position in which the accessory part is prevented from moving further along said guide into the removal position. 
     When the device for locking an electrical device to an accessory part is designed in accordance with the present invention, it has the advantage over the prior art that in locking mechanisms with either a one-stage or a two-stage locking action, the battery pack can be prevented from uncontrollably dropping out of the guide if the user is not holding it or is not holding it correctly when the guide is tilted downward and the release mechanism is intentionally or unintentionally actuated. 
     The present invention is based on the idea that the battery pack locked to the power tool or in general terms, the accessory part locked to the electrical device, after being unlocked and while being moved along the guide out of the locking position and into the removal position, is forcibly deflected into a safety position offset from the guide by means of the break in the guide and the force exerted at this location, and in the safety position, the accessory part is secured in relation to the electrical device until the user grasps it and disengages it from the safety position again, in opposition to the exerted force, in order to then slide it along the guide until it travels all the way into the removal position. 
     Since battery packs are usually removed while power tools are being held in their normal operating position in which the battery pack is pointing downward, the force acting on the accessory part can easily be exerted by the weight of the battery pack if its center of gravity is lower in the safety position than during its movement along the guide and gravity consequently pulls the battery pack downward into the safety position. But since this orientation is not necessarily always maintained and could also be different in other electrical devices, in a preferred embodiment of the present invention, the force acting on the accessory part is a spring force that pushes or pulls the accessory part into the safety position and has the advantage over gravity that it works regardless of the spatial orientation of the components. 
     In another preferred embodiment of the present invention, the spring acts on the accessory part essentially transversely to the movement direction of the accessory part in the guide in order to move the accessory part directly and without deflection of the force direction, into the safety position, in a direction transverse to its movement path in the guide. Even when a spring is used to generate the force required, it is preferable for the safety position to be offset downward in relation to the movement path of the battery pack in the guide in order to provide a redundancy by means of the battery pack&#39;s weight acting on it in the same direction as the force of the spring during the movement of the battery pack into the safety position. 
     Alternatively, however, the spring can also act on the accessory part essentially in its movement direction in order, after the unlocking, to slide it along the guide in the direction of the removal position until, in the break region, the accessory part engages with a suitable guide surface that moves the accessory part, through the action of the spring force and preferably also through the action of its weight, out of the movement path along the guide and into the safety position. 
     According to another preferred embodiment of the present invention, the electrical device and the accessory part are adapted to each other so that in the safety position, the accessory part is in fact prevented from moving toward the removal position, but is able to freely move in the opposite direction toward the locking position so that when being attached to the electrical device, the accessory part can be moved freely all the way into the locking position, even if it is moved into the safety position in the meantime because the user is not holding it correctly. This is preferably achieved by means of the fact that the accessory part and the electrical device are provided with cooperating stop surfaces at one end and are provided with cooperating leading bevels at the other; in the safety position, the stop surfaces are situated opposite one another in the removal direction and prevent the accessory part from being moved further toward the removal position, while the leading bevels are situated opposite from one another in the locking direction and cause the accessory part to be automatically pushed back out of the safety position when the force acting on it has moved it into the safety position while it is being slid into the locking position. 
     In order to provide for a perceptible movement into the safety position in the break region and to simultaneously provide an essentially play-free guided relative movement between the accessory part and the electrical device in the guide both before and after the break, the guide on the accessory part and on the electrical device preferably has alternating projections and recesses; in the region of the break, at least part of the projections engage in the opposing recesses and before and after the break, the respective projections rest against one another with opposing guide surfaces. 
     As in conventional locking mechanisms of power tools and battery packs, the guide is suitably embodied in the form of a linear guide that guides the accessory part on a straight movement path until the break in the guide, where the force exerted on the accessory part causes it to leave the movement path and move into the safety position. Alternatively, however, the guide could also be embodied in the form of a curved guide so that the accessory part is attached to and detached from the electrical device, for example by means of a rotating motion; the safety position is suitably offset in relation to the rotation direction, in the direction that the force is exerted. 
     The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially cutaway perspective view of a first embodiment form of a locking device for locking a power tool to a battery pack; 
         FIG. 2  is a cutaway view of the device from  FIG. 1 , cut along the plane II-II, which shows the battery pack in a locking position; 
         FIG. 3  is a view corresponding to  FIG. 2 , which shows the battery pack during removal from the power tool as it reaches a break in a guide of the locking device; 
         FIG. 4  is a view corresponding to  FIG. 2 , which shows the battery pack in a subsequently assumed safety position; 
         FIG. 5  is a view corresponding to  FIG. 2 , which shows the battery pack after removal from the power tool, in a removal position; 
         FIG. 6  is an enlarged cutaway side view of a second embodiment form of a locking device for locking a power tool and a battery pack together, which shows the battery pack in the locking position, as depicted in  FIG. 2 ; 
         FIG. 7  is a view corresponding to  FIG. 6 , which shows the battery pack during removal from the power tool as it reaches a break in a guide of the locking device; 
         FIG. 8  is a view corresponding to  FIG. 6 , which shows the battery pack in a subsequently assumed safety position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The locking devices  2  shown in the drawings are used to lock a cordless power tool  4 , for example a hand-guided percussion drill, to a battery pack  6  required to supply power to the power tool  4 . 
     As best shown in  FIGS. 1 through 5 , on the free lower end of its handle  8 , the power tool  4  is provided in a known fashion with a protruding guide rail  10  that can be slid in the direction of the arrow A into a guide groove  12  let into the upper end of the battery pack  6 . This guide groove  12  has a cross section complementary to the cross section of the guide rail  10  and, together with it, constitutes a linear guide that defines the predetermined insertion direction (arrow A). 
     The guide rail  10  is provided with two laterally protruding guide strips  14 , whose cross sections essentially correspond to the cross sections of two guide slots  16  (only one of which is visible in  FIG. 1 ) situated opposite from each other inside the guide groove  12 . The tops of the two guide strips  14  are each composed of three projections  18 ,  20 ,  22  with flush, flat tops situated one after the other in the longitudinal direction, between which elongated recesses  24  and  26  are provided. 
     When the guide rail  10  is inserted into the-guide groove  12 , the two guide strips  14  engage with the guide slots  16 , whose upper limit surfaces facing the tops of the guide strips  14  are provided with two elongated recesses  28 ,  30  situated spaced apart from one another in the longitudinal direction, while before, between, and after the recesses  28 ,  30 , the guide slots  16  extend parallel to the tops of the projections  18 ,  20 ,  22  of the associated guide strips  14 . The foremost projection  18  of each guide strip  14  in the insertion direction is sized so that it fits in the hindmost recess  28 , while a protrusion  32  between the recesses  28 ,  30  is sized so that it fits into the recess  24  between the foremost projection  18  and the subsequent projection  20 . 
     The insertion movement of the guide rail  10  into the guide groove  12  is limited by means of cooperating stops  34 ,  36  (see  FIGS. 3 and 4 ), which are situated at the rear ends of the guide rail  10  and guide groove  12  in the insertion direction and rest against each other when the battery pack  6  is properly locked to the power tool  4  in its locking position depicted in  FIG. 2  and an electrical connection is produced between the terminals of a storage battery of the battery pack  6  and an electrical circuit of a consumer of the power tool  4 . 
     As best shown in  FIG. 1 , the locking device  2 , in an intrinsically known manner, has two latches  40  (only one of which is visible), which can be moved in a spring-loaded fashion symmetrical to a vertical central plane of the guide rail  10 , in a transversely extending latch guide and, with their opposing ends, protrude beyond adjacent lateral guide surfaces of the guide strips  14 . When the battery pack  6  is locked to the power tool  4 , the end surfaces of the latches  14  each engage in opposing detent recesses  38  (only one of which is visible) on the inside of the guide groove  12  of the battery pack  6 . In a likewise intrinsically known manner, the locking device  2  has a release mechanism (not shown), which can be manually actuated to disengage the latches  14  from the detent recesses  38  in order to release the battery pack  6 . 
     The locking device  2  can be designed for a one-stage or two-stage locking action; in the latter case, two additional detent recesses (not shown) are provided before the detent recesses  38  in the insertion direction in order to accommodate the latches to secure the battery pack  6  to the power tool  4  without an electrical connection being produced between the terminals of the storage battery of the battery pack  6  and the electrical circuit of the consumer of the power tool  4 . This connection is produced when the battery pack  6  reaches the position shown in  FIG. 2 . 
     To prevent the battery pack  6  from sliding off of the guide rail  10  if the latter is tilted downward counter to the insertion direction (arrow A) and the release mechanism is intentionally or unintentionally actuated without the battery pack  6  being grasped, the guide  10 ,  12  has a break between the locking position and the removal position, which makes it possible to deflect the battery pack  6  out of its linear movement path between the locking position shown in  FIG. 2  and the removal position shown in  FIG. 5 , transversely in relation to the guide  10 ,  12 , into a safety position shown in  FIG. 4 , in which it is prevented from moving further toward the removal position. 
     The break of the guide  10 ,  12  is situated at the point in the movement path of the battery pack  6  at which the projections  18  and  20  on the tops of the guide strips  14  are situated opposite the recesses  28  and  30  in the upper limit surfaces of the guide slots  16  and the protrusions  32  in the upper limit surfaces of the guide slots  16  are situated opposite the recesses  24  in the tops of the guide strips  14 , as shown in  FIG. 3 . In this position, the weight of the battery pack  6  pulls it downward (arrow G), causing the projections  18  and  20  to engage in the recesses  28  and  30  and the protrusions  32  to engage in the recesses  24 . 
     At their rear ends in the insertion direction, the projections  18  have stop surfaces  42  that are perpendicular to the insertion direction and, in the safety position, are situated opposite complementary stop surfaces  44  of the recesses  28  so that they prevent the battery pack  6  from moving further toward the removal position, as shown in  FIG. 4 . In order to disengage the battery pack  6  from the safety position for removal, it only needs to be lifted slightly in the direction of the arrow B and then moved again further in the guide  10 ,  12  until it reaches the removal position. 
     By contrast, at their front ends in the insertion direction, the projections  18 ,  20 , and  22  are bounded by leading bevels  46 ,  48 ,  50 , which in the safety position, are situated opposite complementary leading bevels  52 ,  54  of the recesses  28 ,  30 . This allows the battery pack  6  to be slid unhindered into the locking position, even if it is not held correctly by the user and moves into the safety position as a result. 
     Whereas with the locking device  2  shown in  FIGS. 1 through 5 , the movement of the battery pack  6  into the safety position is initiated by the force of gravity on it, with the locking device  2  shown in  FIGS. 6 through 8 , two prestressed leaf springs  60  are also provided in order to tilt the battery pack  6  in relation to the power tool  4 , into the safety position shown in  FIG. 8  when it reaches the break in the guide  10 ,  12  ( FIG. 7 ). The leaf springs  60  are inserted into the battery pack  6  underneath the guide slots  16  so that they press from underneath against the underside of the adjacent guide strips  14  and press the adjacent guide surfaces  62 ,  64  of the guide groove  12  and guide rail  10  apart from each other when the break in the guide  10 ,  12  is reached. The projections  18  are brought into engagement with the recesses  28  and the protrusions  32  are brought into engagement with the recesses  24  as described above. 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in a device for locking an electrical device to an accessory part, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will reveal fully revela the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of the invention.