Abstract:
A battery clamp comprises a contact ring that can be placed on a battery contact of a battery to be connected, a spring ring capable of pressing the contact ring against the battery contact, and a press-on housing capable of pressing the spring ring against the contact ring. There is further proposed a battery which is particularly suitable for being used in combination with such a battery clamp.

Description:
TECHNICAL FIELD 
     The invention relates to a battery clamp by means of which a battery can be connected, in particular a vehicular starter motor battery, as well as to a battery which is particularly suitable for being used in combination with such a battery clamp. 
     BACKGROUND OF THE INVENTION 
     The problem during making contact with a battery contact is that for a reliable contacting there has to be maintained a defined contact force as precisely as possible. With the contact forces being too low, there will only be produced an insufficient metal-to-metal contact between battery contact and battery clamp. If, however, there are applied contact forces which are too high, this will result in a deformation and flowing of the battery contact material. 
     The most common battery clamp is comprised of a contact strap which is placed on the battery contact and subsequently is pulled tight by means of a screw bolt. It is a disadvantage with this type of battery clamp that the contact force which in fact is applied can be monitored only in an insufficient way. On the one hand, there is the danger that, by pulling tight of the screw bolt with a wrench, a much higher tightening moment and, thus, a much higher contact force is applied than would be actually required. On the other hand, there is the danger that, whenever the battery clamp is used with an already deformed battery contact, the contact strap is pulled to block by the screw bolt, so that a high tightening moment will be obtained for the screw bolt which, however, does not correspond with the lower contact force that will be achieved actually. 
     From prior art there are further known various battery clamps which employ spring elements that are intended to guarantee a constant contact force. These battery clamps, however, are of a comparably complicated construction. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore it is the object of the invention to provide a battery clamp which is able to be manufactured in a simple and cost-effective manner and at the same time is fail-proof in terms of process, i.e. a battery clamp which can be assembled with high reliability both manually and in an automated way, without the danger of faulty assembly occurring. It is further the object of the invention to further develop the known vehicle batteries to the effect that they are able to be implemented with such a battery clamp. 
     According to the invention, a battery clamp is provided which comprises a contact ring that can be placed on a battery contact of a battery to be connected, a spring ring capable of pressing the contact ring against the battery contact, and a press-on housing capable of pressing the spring ring against the contact ring. This battery clamp is based on the basic idea to use as few components as possible, which are of a simple construction and are optimally adapted to the function which is to be fulfilled by them. The contact ring, to which a battery cable may be crimped, serves exclusively for contacting the battery contact. The contact force by means of which the contact ring can be elastically pressed against the battery contact is provided by the spring ring. The press-on housing has merely the task to press the spring ring onto the contact ring. 
     According to the preferred embodiment it is provided for that the contact ring is provided with several elastic contact tabs that together form a ring, the middle axis of which is coincident with the middle axis of the battery contact to be contacted. In this arrangement, it is preferably provided for that the contact tabs are curved, so that they touch the battery contact in a region which is spaced from their free end at which the spring ring engages. Furthermore, it is preferably provided for that the free ends of the contact tabs are bent, so that the ring defined by the contact tabs has a slope surface at which the spring ring engages. With this design of the contact tabs, the spring ring may be slipped on the slope surface of the ring that is formed by the contact tabs, so that the contact tabs are elastically prestressed. The elastic prestress of the contact tabs is possible, because their point of contact with the battery contact is spaced from that region at which the spring ring engages the contact tabs. The prestress of the spring tabs adds to the prestress through the spring ring, so that even with settling phenomena between the contact tabs and the battery contact, there will be maintained a sufficient contact force over a long period of time. 
     According to the preferred embodiment of the invention it is provided for that the contact ring is provided with several holding lugs by means of which it is latched in place on the press-on housing. It is further provided for that the press-on housing is provided with several detent tabs which cooperate with the holding lugs. In this way, the press-on housing and the contact ring are joined into a unit. 
     According to the preferred embodiment of the invention, there is provided a press-on lid to which the press-on housing is attached. The press-on lid fulfills a number of functions. It can be provided with a projection which is able to engage into a recess in a skirt of a battery to be connected. It is in this way that there is made use of a lever effect by means of which the force can be increased which is applied by the press-on lid via the press-on housing onto the spring ring. Further, there can be provided a locking tab on the press-on lid, which locking tab is able to engage a skirt of a battery to be connected. This allows to lock the entire battery clamp on the battery. 
     According to the preferred embodiment it is provided for that the press-on lid is provided with two elongated slots and the press-on housing is provided with two pins which engage in the elongated slots. In this arrangement, the pins preferably lie on a line which intersects the middle axis of the battery contact to be contacted. This ensures that there will not occur any tilting forces during pressing on of the press-on housing, as the spring ring is loaded symmetrically. 
     According to the preferred embodiment of the invention there is provided a blocking tab which in a blocking position extends as far as into the space that is occupied by the battery contact, the blocking tab preventing in the blocking position the spring ring from being slipped on the contact ring, and the blocking tab being able to be brought by the battery contact into a release position in which the spring ring can be slipped on the contact ring. Thus, the blocking tab increases the process safety to this effect that the spring ring can only be slipped on the contact tabs of the contact ring if the contact ring is placed on a battery contact. An unintentional “closing” of the battery clamp prior to being correctly placed on a battery contact is prevented. 
     The above object is also solved by a battery that is wherein there are provided a battery contact and a skirt, the skirt surrounding the battery contact. On the one hand, the skirt serves as a mechanical protection for the battery contact. On the other hand, it opens new possibilities of fastening the battery clamp. The skirt may be provided with a recess, for example, which can be engaged by the projection of the press-on lid of the battery clamp. Furthermore, the skirt may be provided with a shoulder which can be engaged by the locking tab of the press-on lid of the battery clamp. 
     It is preferably made provision that the skirt is provided with a cut-out through which a connecting section of a contact ring extends, the contact ring being provided with a stop that cooperates with the skirt, so that a strain relief is produced. This makes sure that any forces that act on the connection cable, are not transferred to the battery contact and the battery clamp. Advantageous designs of the invention will be apparent from the sub-claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows in a schematic, broken view a battery with the placed-on battery clamp in the open state; 
     FIG. 2 shows the battery and the battery clamp of FIG. 1 in the closed state; 
     FIG. 3 is a partial top view onto the battery with the battery clamp being placed on, with all parts of the battery clamp having been removed except of the contact ring; 
     FIG. 4 is a schematic top view onto the battery with the battery clamp taken off; 
     FIG. 5 is a perspective, partial view of the battery; 
     FIG. 6 shows in a schematic view a battery contact with the contact ring placed on; and 
     FIG. 7 shows the battery clamp in a bottom view. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     First, the battery will be described by means of FIG.  3 . This battery concerns a vehicular starter motor battery, through which may be delivered electric energy to a starter motor of a combustion engine of a motor vehicle. The battery, here referenced by reference numeral  5 , usually has two battery contacts  10  of which only one is shown here. The relative arrangement of the battery contacts to each other as well as the design of the battery is not of importance here, so that the battery is only indicated schematically and in sections here. 
     Unlike with conventional battery contacts, the battery contact  10  is designed to be cylindrical (see in particular FIGS. 1 and 2) and is merely provided with a comparably short conical section  12  at its end. With a cylindrical battery contact, there will not occur any forces acting in longitudinal direction of the battery contact if a battery clamp is being placed on it. 
     The battery is provided with a skirt  14  which completely surrounds the battery contact. The skirt  14  is provided with two cut-outs  16  which with respect to the middle axis of the battery contact are arranged at an angle of 90° relative to each other. The function of the cut-outs  16  will be explained later. Further provided in the skirt  14  is a recess  18  (see FIG.  5 ), and a shoulder  20  is formed on the skirt. The function of recess  18  and shoulder  20  will likewise be explained later. 
     The essential components of the battery clamp are a press-on housing  22 , a spring ring  24  as well as a contact ring  26 . 
     The contact ring  26  (see in particular FIGS. 3,  6  and  7 ) consists of a sheet metal having a contact portion  28  and a connecting portion  30 . The contact portion  28  serves for contacting the battery contact  10 , and the connecting portion  30  serves for connecting a battery cable  32 , for instance by crimping. 
     The contact portion  28  is provided with several contact tabs  34  lying side by side, which are bent upwards by approximately 90° from the plane of the connecting portion (see in particular FIGS.  1  and  2 ). All the contact tabs  34  together form a discontinuous ring which concentrically surrounds the battery contact to be contacted. Here, each individual contact tab is bent such that the smallest diameter of the ring which is formed, that is the region resting at the battery contact, is situated approximately in the middle between the material ring which connects the contact tabs which each other, and the free end of the contact tabs. The free end  36  of each contact tab is bent such that all the contact tabs together form a discontinuous slope surface that can be engaged by the spring ring  24 . 
     Finally, the contact ring  26  is provided with three holding lugs  38  which cooperate with corresponding detent tabs  40  on the press-on housing  22 , in order to secure the contact ring  26  to the press-on housing  22 . 
     The press-on housing  22  consists of plastics material and is provided with a blocking tab  42  (see FIG. 1) which in a blocking position may extend as far as into the space that can be occupied by the battery contact  10 . In the blocking position, the blocking tab  42  prevents that the spring ring  24  is able to be slipped on the contact tabs  34  of the contact ring  26 , if the battery clamp is not properly arranged on a battery contact. If the battery clamp is properly placed on the battery contact  10 , then the blocking tab  42  will be forced outwards by the latter into a release position in which the battery clamp can be firmly attached to the battery contact. 
     The press-on housing  22  is provided with a press-on ring  44  which supports the spring ring  24 . To this end, the press-on ring  44  is provided on its inner side with a slightly raised edge. Provided on the press-on housing  22  are several spring tabs  46  which engage on the spring ring  24  and hold it on the press-on ring  44 . 
     Attached to the press-on housing  22  is a press-on lid  48  which completely covers the press-on housing  22  on its outside. The press-on lid  48  is provided with two side elements  50 , with an elongated hole  52  being formed in each of these side elements. Each elongated hole  52  is engaged by a pin  54  formed on the press-on housing  22 . The press-on lid  48  is further provided with a projection  56  which engages into a recess  18  in the skirt  14  of the battery. On the opposite side, the press-on lid  48  is provided with a locking tab  58  which is able to cooperate with the shoulder  20  on the skirt  14  of the battery. 
     The battery clamp described is assembled in the following way: First, the spring ring  24  is placed on the press-on ring  44  in the press-on housing  22  where it is held by the spring tabs  46 . Then, the contact ring  26  is mounted such that the holding lugs  38  of the contact ring snap in place behind the detent tabs  40  of the press-on housing  22 . Finally, the press-on lid  48  is placed on the press-on housing  22  in such a manner that the pins  54  engage the elongated holes  52 . 
     For reliably connecting all components with each other, only simple working steps are necessary for assembling the battery clamp, because the components automatically latch into each other, so that a completely assembled unit is obtained. 
     The battery clamp is mounted to the battery in the following way: The battery clamp is inserted in the skirt such that the projection  56  engages into the recess  18  and the connecting portion  30  of the contact ring  26  extends through one of the cut-outs  16  of the skirt. Due to the fact that there are provided two cut-outs, it is ensured that the connecting portion and the battery cable  32  connected thereto always extend in a direction which is suitable for the particular mounting situation. The contact ring  26  is designed such that the connecting portion  28  on the inside of the skirt rests at both sides of the cut-out  16 , so that a strain relief is established. Alternatively, a stop may also be provided on the contact ring  26 , which stop rests at the skirt  14 . 
     Immediately after insertion of the battery clamp into the skirt  14  of the battery, the battery clamp is in the condition shown in FIG.  1 . The press-on lid  48  extends slightly upwards, and the spring ring  24  is spaced from the contact tabs  34  of the contact ring  26 . If desired, the battery contact  10  and the contact tabs  34  may be sized with respect to each other such that, already in this condition, the contact tabs rest at the battery contact with a slight prestress. 
     In order to finish mounting of the battery clamp, the press-on lid  48 —starting from the condition shown in FIG.  1 —is forced downwards into the position shown in FIG. 2, until the locking tab  58  snaps in place behind the shoulder  20  of the skirt  14 . In so doing, the press-on housing  22  is forced downwards with respect to FIGS. 1 and 2, so that the spring ring  24  is slipped on the free ends  36  of the contact tabs  34 . Simultaneously, the spring ring  24  which is conically expanded on its side facing the contact tabs  34 , presses the contact tabs  34  against the battery contact in an elastic fashion, so that the required contact force is produced at that place. As can be seen from FIG. 2, the spot of contact between the contact tabs  34  and the battery contact  10  is spaced by a distance D from the region of contact between the contact tabs  34  and the spring ring  24 . This distance D results in the contact tabs  34  being elastically prestressed. Hence, the battery clamp has a large reserve which allows to compensate for any settling processes between the battery contact  10  and the contact tabs  34 . 
     The press-on lid  48  is designed such that it completely covers the region of the battery lying within the skirt  14  and consequently the battery contact  10 . Furthermore, the press-on lid  48  can be designed such it largely closes the cutouts  16  in the skirt  14 . An erroneous contacting with contact cramps, for example, is prevented since the battery contact is completely covered by the skirt  14  and the press-on lid  48 . 
     For disconnecting the battery clamp, the locking tab  58  is pulled outwards, so that it comes off the shoulder  20 . Subsequently, the press-on lid  48  can be pulled off in upward direction, which entrains the press-on housing  22  and the spring ring  24 . With this, the contact tabs  34  are freed and the battery clamp can be pulled off from the battery contact.