Patent Publication Number: US-8534254-B2

Title: Starter device

Description:
The invention relates to a starter device for an internal combustion engine of a manually guided engine unit, wherein the device comprises a housing and a cable drum which can be rotated relative to the housing about a rotational axis with a starter pull for starting the engine, and has a recoil spring space, which is arranged between the housing and the cable drum, for a recoil spring, in order to move the cable drum into its original position after a rotational movement of the starter, wherein a seal is provided for sealing off the recoil spring space. 
     Internal combustion engines of manually guided engine units are generally started with cable pull starters. In this case a rotary movement is transferred to the crankshaft by means of a starter device consisting of a starter handle, a starter cable, a cable drum, a housing and a suitable coupling. This rotary movement is produced by pulling the starter cable away from the cable drum. The rotary movement produced thereby is transferred by means of the coupling to the fan impeller which is connected in a force-fitting manner to the crankshaft. 
     This fan impeller has the task of providing the internal combustion engine with enough cooling air. The volumetric flow which is conveyed in the direction of the center of the engine is taken from the environment via the housing. Depending on the application, engine type, ambient conditions etc., the ambient air can be contaminated to differing extents by for example dust or chippings. In order to guarantee functioning of the starter device in the long term, it is necessary to protect the affected components extensively from dirt. 
     A starter device of this type is disclosed in DE 197 25 901 A1. In this design an intermediate piece must be present between the cable drum and the ventilator housing. This forms a partition of the recoil spring space and holds a labyrinth seal. This has a pair of mutually opposite clamping jaws so that fastening to the ventilator housing is possible by means of screw fastenings. For sealing purposes a lip must also be present which surrounds the intermediate piece and thus seals off the outside of the intermediate piece as far as the ventilator housing. In addition to the wall which forms the space, there is a further, cylindrical wall which runs inwards parallel to the bearing axis. The partition extends radially inwards from a transition between a flange and the cylindrical wall. The partition forms the inner wall for the recoil spring space. 
     With this solution two seals are in principle required: a labyrinth seal and an outer sealing lip. An additional partition must also be attached. 
     The invention is based on the object of creating a starter device which on the one hand prevents dirt from penetrating into the recoil spring space and on the other hand has a simple design. 
     This object is achieved by a device with the features of claim  1 . 
     The invention is based on the finding that, in a cable starter which is known per se, the cover of the recoil spring which is proposed according to DE 197 25 901 A1 can be omitted. The sealing of the installation space for the recoil spring, which is now produced between the outside of the cable drum and the inside of the housing, is sealed off according to the invention by a sealing medium between the housing and the cable drum. 
     The invention means that no intermediate wall is necessary between the cable drum and the recoil spring space. Instead of equipping the intermediate wall with a sealing element in order to prevent dust and other foreign material from being able to penetrate into the recoil spring space from the environment via passages between the cable drum and the recoil spring space, a sealing arrangement is placed on opposite sides directly between the housing and the cable drum. A compact construction is thus achieved owing to the optimisation of installation space. 
     The invention is based on the idea of moving the seal for sealing off the recoil spring space from a partition, which can now be omitted according to the invention, to the outer wall of the housing. 
     The invention has the advantage that the design is much simpler and therefore more cost-effective and optimised in terms of weight because fastening of an intermediate piece with screw fastenings can be omitted. In addition, two seals with sealing lips do not have to be used. It is therefore possible to use a single seal which prevents penetration of dust and the like into the recoil spring space and into the bearing point. 
     Further advantageous configurations of the invention are characterised in the dependent claims. 
     According to one development of the invention, it is provided for the cable drum to form an inner wall for the recoil spring space. 
     In one advantageous development of the device according to the invention it is provided for the cable drum to be provided with a connecting web which is aligned axially towards the housing and forms a wall of the cylindrical disc-shaped recoil spring space on one side and bears the seal on the other side. This embodiment simplifies the formation of the recoil spring space in that an inner face of the connecting web forms an inner outer wall of the space. The seal can be arranged relatively far outwards on a face of the connecting web which is perpendicular to the axis of rotation and on a face which is opposite the housing, so that outer protection from dust and other contamination is provided. 
     The cable drum is mounted in a simple manner in that the housing is provided with a bearing pin on which the cable drum is mounted. 
     In a further advantageous embodiment of the invention the seal is arranged radially outside the recoil spring space. Whereas the recoil spring space is situated in a central region of the cable drum, the seal is located outside the space in a separate region, viewed virtually radially. The recoil spring space and the seal are spatially separated from each other. 
     The cable drum is expediently configured as a spring holder for the recoil spring because an intermediate part to which the recoil spring could be fastened can then be omitted. 
     It is advantageous if the wall of the recoil spring space which is associated with the housing is formed by a disc-shaped covering element of the housing, which is connected in a detachable and/or non-rotating manner to a base body of the housing. This means that a flat bearing face for the recoil spring and an inner wall for the recoil spring space is created. The fastening of the covering element can be achieved in that the bearing pin has a radial web which engages in a cut-out in a bearing opening of the covering element in order to fix the latter in a non-rotating manner. 
     The seal can be configured as a contactless seal, in particular as a labyrinth seal, or as a sealing lip, sealing ring, rubber ring or felt ring. 
     According to an advantageous embodiment, the housing is formed as a ventilator housing. 
     It is particularly advantageous if the recoil spring is mounted in a spring cartridge which is arranged in the recoil spring space which is completely surrounded by the housing and the cable drum. 
     In contrast to the known prior art, only a single seal is present. 
    
    
     
       An exemplary embodiment is explained in more detail on the basis of the drawings, advantageous developments of the invention and advantages of the same being described. In the figures, in a purely schematic representation: 
         FIG. 1  shows a perspective view of a device according to the invention, 
         FIG. 2  shows a sectional view of a first embodiment of the device according to the invention, 
         FIG. 3  shows a sectional view of a second embodiment of the device according to the invention, 
         FIG. 4  shows a sectional view of a third embodiment of the device according to the invention, and 
         FIG. 5  shows a sectional view of a fourth embodiment of the device according to the invention. 
     
    
    
     In the figures the same parts are given the same reference symbols. 
       FIG. 1  shows a starter device  100  for an internal combustion engine of a manually guided engine unit, for example a power saw. The device comprises an immovable housing  10  and a cable drum  11  which can be rotated relative to the housing  10  about a rotational axis X. The cable drum is connected to a starter pull for starting the engine. To this end a cable  12  and a handle  28  are arranged in a known manner. 
     As shown in  FIG. 1 , a recoil spring  13  is present between the housing  10  and the cable drum  11 . The spring  13  is embedded in a recoil spring space  14 , as can be seen in  FIG. 2 . The recoil spring  13  has the task of moving the cable drum  11  into its original position after a rotational starter movement. 
     According to the invention, a seal  15  is situated directly between the cable drum  11  and the housing  10  for sealing the recoil spring space  13  to prevent dust, chippings or other dirt from penetrating into the space  14  or even into the bearing. The seal  15  is thus spaced radially apart from the rotational axis X to such an extent that the recoil spring space  13  is formed by a wall  16  of the cable drum  11  and an approximately opposite wall  17  of the housing  10 . The cable drum  11  forms according to the invention an inner wall  16  for the recoil spring space  14 . The seal  15  is also arranged radially outside the recoil spring space. The cable drum is configured as a spring holder for the recoil spring. 
     As shown further in  FIG. 2 , the cable drum  11  is provided with a connecting web  18  which is directed axially towards the housing  10 . This web forms a wall  27  of the cylindrical disc-shaped recoil spring space  14  on one side and bears the seal on the other side. 
     For mounting purposes the housing  10  is provided with a bearing pin  19  on which the cable drum  11  is mounted. 
       FIG. 1  shows a covering element  20 , with this belonging to the housing  10 . The housing  10  thus consists of a base body  21  and the covering element  20 . The wall  17  of the cable drum which is associated with the housing  10  is formed by a disc-shaped covering element of the housing which is connected in a detachable and non-rotating manner to a base body of the housing. The bearing pin  19  has a radial web  22  which engages in a cut-out  23  in a bearing opening of the covering element  20  in order to fix the latter in a non-rotating manner. 
     In an embodiment shown in  FIG. 2 , the seal is configured as a labyrinth seal  24 . A labyrinth seal means a contactless seal, the sealing effect of which is based on the sealing gap being relatively long and at the same time extremely narrow, so that in the present case the ingress of dirt is largely reduced. The cable drum  11  is provided with labyrinth webs which are directed axially in the direction of the housing  10  and dip into annular grooves formed on the housing  10 . 
     In another embodiment which is shown in  FIG. 3 , the seal comprises at least one sealing lip  25 . This is arranged in the region of the outer edge of the cable drum  11 . 
       FIG. 4  shows a variant in which the seal comprises at least one annular seal  26  such as a rubber ring, felt ring or radial shaft seal. This is embedded in an annular groove which is directed towards the housing  10 . 
       FIG. 5  shows a variant, the basic structure of which corresponds to the embodiment according to  FIG. 2 , but in which an inner spring cartridge  29  is provided. 
     The above-described starting system is provided with a recoil spring  13  which effects rewinding of the starter cable onto the cable drum  11  and thus rotating back into the original position after every individual starting attempt. This also means that further rapidly successive starting attempts are possible and that the unwound starter cable is pulled back into the cable drum immediately after every starting attempt so that it does not become caught in moving parts. 
     Owing to the explained design, the functioning of the recoil spring  13  can be ensured and the latter can be in particular protected from dirt. 
     The recoil spring  11  is practically not encapsulated in a separate spring cassette, but to be positioned in the contour of the spring space between the cable drum and the housing. This means that sealing can take place between the housing  10  and the cable drum  11  which protects the recoil spring  13  from dirt before action. 
     The invention is not limited to this example, for instance, although only one seal is present in each case in the figures, a plurality of seals, for example two annular seals or a combination of seals, for example a labyrinth seal and a sealing lip, can be used. 
     LIST OF REFERENCE SYMBOLS 
       10  Housing 
       11  Cable drum 
       12  Cable/starter cable 
       13  Recoil spring 
       14  Recoil spring space 
       15  Seal 
       16  First wall 
       17  Second wall 
       18  Connecting web 
       19  Bearing pin 
       20  Covering element 
       21  Base body 
       22  Radial web 
       23  Cut-out 
       24  Labyrinth seal 
       25  Sealing lip 
       26  Annular seal 
       27  Third wall 
       28  Handle/starter handle 
       29  Inner spring cartridge 
       100  Starter device 
     X Axis of rotation