Patent Publication Number: US-2011056443-A1

Title: Back-carried work apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority of German patent application no. 10 2009 040 494.5, filed Sep. 8, 2009, the entire content of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates to a back-carried work apparatus. 
     BACKGROUND OF THE INVENTION 
     Back-carried work apparatuses typically have an elongated tank extending over the entire width of the work apparatus. A suction head is typically provided to draw fuel. For the suction head to be able to deliver fuel, a minimum fill level of the fuel is needed in the area of the suction head. Because the base of the tank is typically essentially even, a comparatively large residual amount of fuel cannot be drawn even on work apparatuses which are carried horizontally. The amount of fuel which cannot be extracted can become noticeably larger when the back carrier is not carried horizontally, for example, when the operator only has one shoulder strap on one shoulder, so that the entire back carrier is slanted. When the suction head is in a disadvantageous position a comparatively large amount of fuel cannot be extracted. As a result, frequent filling of the fuel tank is necessary, which considerably reduces the effective working time. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a back-carried work apparatus, in which the drawing of fuel is possible up until only a small amount of residual remains and which has a simple configuration. 
     The back-carried work apparatus of the invention includes: a back carrier having two shoulder straps configured for carrying the back carrier on an operator&#39;s shoulders; a drive motor configured as a combustion engine arranged on the back carrier; a fuel tank for the combustion engine arranged on the back carrier, the fuel tank having a tank base; the tank base having a width (d) and being configured to have a lowest region when the shoulder straps are arranged on the operator&#39;s shoulders; and, the lowest region extending over less than about 20% of the width (d) of the tank base. 
     The lowest area, which is formed comparatively narrowly, leads to a higher fill level with the same amount of fuel when compared to a fuel tank with an even base, so that also residual amounts can be easily drawn. Therein, it is advantageous to arrange means for drawing fuel in the lowest area. 
     A simple configuration results when the tank base has a first section, which is inclined relative to the horizontal level when the shoulder straps are arranged on the shoulders of an operator. The first section of the tank base is inclined relative to the horizontal level by an angle between about 7° and about 30°. The angle is advantageously chosen in such a manner that the first section remains inclined toward the center or at maximum is horizontal when the operator carries the back carrier only with the shoulder strap across from first section and the back carrier is therefore slanted on the back of the operator. Since the first section does not noticeably slope down toward the outside it is ensured that even when the back carrier is carried slanted and the fill level of the fuel is low, fuel can still be extracted. The first section advantageously slopes down toward the center of the tank base. Advantageously, a second section of the tank base is inclined in the opposite direction of the first section. The second section of the tank base is thereby also advantageously inclined relative to the horizontal level at an angle between about 7° and about 30°. In particular, the inclination of the first section of the tank base corresponds to the inclination of the second section. The lowest area is advantageously arranged between the first section and the second section and in the center of the tank base in relation to the width of the tank. 
     Advantageously, a middle section is arranged between the first section and the second section, which extends over less than 30% of the width of the tank base and includes the lowest area. The tank base in the middle section can advantageously be rounded. Thereby edges, on which a suction head or similar device for extracting fuel can become stuck on, are avoided in the tank base. This results in an attractive appearance of the fuel tank. Advantageously, the tank base is mirror-symmetrical to a center plane extending in the upward direction of the back carrier. The center plane thereby extends approximately perpendicularly to the plane of the operator&#39;s back and approximately vertically when the back carrier is carried straight. 
     It can also be provided that the first section slopes down from one side wall of the fuel tank to the other and that the lowest area is arranged adjacent to the side wall to which the first section slopes down towards. The fuel tank is thereby configured asymmetrically and the lowest area is arranged on the side. Advantageously, the work apparatus has an operating handle to guide the work apparatus while in operation and the lowest area is arranged on the side of the fuel tank which faces the aforementioned handle. When the back-carried work apparatus is carried with only one shoulder strap, the shoulder strap on the side facing away from the handle is typically on the shoulder, so that the work apparatus slopes down toward the side facing the handle. As a result of the inclination of the base of the fuel tank toward this side and the advantageous arrangement of means to extract fuel in this lateral area it can be ensured that a comparatively large amount of fuel can always be extracted from the fuel tank and only a very small amount of residual remains in the tank when the work apparatus is carried straight as well as when the work apparatus is carried by the shoulder strap on the opposite side of the handle. 
     To achieve a high fill level with small amounts of fuel in the tank, the sloped sections of the tank base extend over more than 70% of the width of the tank base of the fuel tank. More than two sloped sections can also be provided therein. 
     Advantageously, the tank base is inclined in the direction of the center plane in at least one area. In that the tank base is inclined in the direction of the center plane, that is, in the direction of the depth of the fuel tank, the amount of fuel which cannot be extracted from the fuel tank can be further minimized. 
     The fuel tank can be largely emptied. Advantageously, the tank base is configured in a funnel-like manner. Thus, all base surfaces are inclined toward the lowest area. 
     Advantageously, the fuel tank has a transverse plane which divides the fuel tank in the middle into a section facing the operator and a section facing away from the operator. The transverse plane thus typically runs parallel to the back carrying plate of the back carrier. Advantageously, the lowest area is arranged in the section facing away from the operator. During typical operation, the back carrier tilts back away from the back of the operator and rests against the back of the operator in its lower area. In that the lowest area is arranged in the externally located area of the fuel tank facing away from the operator, which during typical operation tilts downward, a good fuel extraction can be achieved. 
     The proposed configuration is especially advantageous in elongated tanks. The fuel tank has an advantageous width, which is at least double the height measured in the upward direction and at least double the depth of the fuel tank which is measured perpendicularly to the width and to the height. The back carrier advantageously has a base plate which extends in the direction of the horizontal level when the shoulder straps are arranged on the shoulders of the operator. The base of the fuel tank is thereby inclined relative to the base plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to the drawings wherein: 
         FIG. 1  is a side view of an operator with a back-carried work apparatus; 
         FIG. 2  is a side view of the work apparatus in the direction of arrow II of  FIG. 1 ; 
         FIG. 3  is a side view of the work apparatus according to  FIG. 2 , when the back carrier is carried by only one shoulder strap; 
         FIG. 4  is a side view of the work apparatus according to 
         FIG. 2 , when the back carrier is carried by only one shoulder strap; 
         FIG. 5  is a sectionally enlarged side view of the work apparatus in the area of the fuel tank; 
         FIG. 6  is a side view of the work apparatus; 
         FIG. 7  is a sectionally enlarged side view of an embodiment of the fuel tank. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
       FIG. 1  shows as an example embodiment a blower  1  as a back-carried work apparatus. The blower  1  has a back carrier  2  which is carried on the back of an operator  14  with the shoulder straps  3  and  4  ( FIG. 2 ). The back carrier  2  includes a back carrier plate  15 , which advantageously rests on the back of the operator  14  and can be braced against the back via pads, as well as a base plate  16 . A housing  5  of the blower  1  is held on the back carrier  2 . The blower  1  has a fuel tank  7  which is arranged underneath the housing  5 . The fuel tank  7  can, however, also be arranged in the housing  5  or be integrated into the housing  5 . As  FIG. 1  shows, a start handle  6  of a starting arrangement projects out of the housing  5 . The blower  1  has a blower tube  12  on which an operating handle  13  is arranged. The operator  14  can hold and guide the blower tube  12  via the operating handle  13  with one hand  26 , here with the right hand  26 . 
     The start handle  6  serves to start a drive motor  20  arranged in the housing  5 , which is shown schematically in  FIG. 2 . The drive motor  20  is configured as an internal combustion engine. During operation, the drive motor  20  draws in fuel from the fuel tank  7 . When the operator  14  carries the back carrier  2  with both shoulder straps ( 3 ,  4 ), then the base  19  of the back carrier  2  is arranged horizontally and aligns with the horizontal line H. The tank  7  has a tank base  8  having a first inclined section  9  and a second inclined section  10 . A middle section  11  is arranged between the two inclined sections  9  and  10 . 
     The first section  9  is inclined relative to the horizontal line by an angle α, which advantageously is between about 7° and about 30°. An angle α between about 10° and about 20° has proven to be expedient. The angle α is chosen so that the tank base  8  slopes down in the first section  9  toward the middle section  11 . The second section  10  is inclined relative to the horizontal line H by an angle β, which is between about 7° and about 30° and advantageously between about 10° and about 20°. Advantageously, the angles α and β are the same size and the tank base  8  is mirror-symmetrical to a center plane  22  running in the upward direction  21  of the blower  1  and about perpendicularly to the back carrier plate  15 . The upward direction  21  is essentially vertical when both shoulder straps  3  and  4  are arranged on the shoulders of the operator  14 . 
     In the area of the middle section  11 , a suction head  18  is arranged in the interior of the fuel tank  7 , via which fuel is taken from the fuel tank  7  and drawn to the drive motor  20 . As also shown in  FIG. 2 , the back carrier plate  15  has a handle  17  with which the back carrier  2  can be carried by hand. 
       FIGS. 3 and 4  show the back carrier  2  carried by only one shoulder strap, namely with the right shoulder strap  3  in  FIG. 3  and with the left shoulder strap  4  in  FIG. 4 . If the back carrier  2  is carried only with the right shoulder strap  3 , the entire back carrier  2  in  FIG. 3  tilts counter-clockwise, whereby the outer area of the second section  10  is inclined down and runs approximately horizontally. The first section  9 , which is arranged underneath the right shoulder strap  3 , is more inclined. The angle β is chosen such that the second section  10  is arranged approximately horizontally when the back carrier is carried by the right shoulder strap  3 , so that the suction head  18 , arranged in the middle section  11 , is still supplied with fuel. Thereby, the bulk of the fuel in the fuel tank  7  can be drawn when the blower  1  is carried at an angle. 
     If, as shown in  FIG. 4 , the back carrier  2  is carried with the left shoulder strap  4 , the first section  9  is arranged approximately horizontally, and the second section  10 , arranged underneath the left shoulder strap  4 , is more inclined. Here as well, the suction head  18  is still supplied with fuel even when the amount of fuel, which is needed for a minimum fill level, is increased relative to when the back carrier is carried horizontally ( FIG. 2 ). As a result of the inclination of the tank base in sections  9  and  10 , it is avoided that the suction head  18  is not supplied with a sufficient amount of fuel when only little fuel has been drawn. More specifically, the situation is prevented that the suction head comes to lie in an area of the fuel tank  8  in which there is no fuel or an insufficient fill level of fuel. 
       FIG. 5  shows the configuration of the fuel tank  7  in detail. The fuel tank  7  has a width (b) which is at least twice as large as the height (a) measured in the upward direction  21  ( FIG. 2 ). The width (b) and the height (a) are thereby the entire width and the entire height of the fuel tank  7 , respectively. The tank base  8  has a width (d). The first section  9  has a width (e) and the second section  10  has a width (f). The width (e) and the width (f) together extend over 70% of the width (d) of the tank base  8 . Advantageously, the sections  9  and  10  extend over at least 90% of the width (d). The middle section  11  extends over a width (g) which is at most 30% of the width (d) of the tank base  8 . Advantageously, the width (g) is less than 20%, especially less than 10%, of the width (d) of the tank base  8 . 
     The first section  9  and the second section  10  decline toward the middle section  11 . The first section  9  thereby borders laterally on a first side wall  24  of fuel tank  7  and the second section  10  borders laterally on a second side wall  25 . The middle section  11  includes a lowest region  23  of the tank base  8 , which is the lowest point of the fuel tank  7  when the base  19  of the back carrier  2  is arranged horizontally. The suction head  18  is arranged in the lowest region  23 . The lowest area  23  is configured as small as possible and advantageously extends over less than 20% of the width (d) of the tank base  8 . In the embodiment the width (i) of the lowest region  23  is about 3% of the width (d) of the tank base  8 . 
     As  FIG. 6  shows, the base  8  of the fuel tank  7  is noticeably inclined in its depth, that is, perpendicular to the upward direction  21  of the blower  1  and perpendicular to the width (d). The tank base  8  is in the middle section inclined at an angle (Y), which advantageously is at least 5°, relative to the horizontal line H. As  FIG. 6  shows, the fuel tank  7  has an imaginary transverse plane  30 , which divides the fuel tank  7  in its depth in the middle. The transverse plane  30  runs approximately parallel to the back carrier plate  15 . The transverse plane  30  divides the fuel tank  7  into a section  31  facing the operator and a section  32  facing away from the operator. The section  32  projects outwardly in the embodiment. As  FIG. 6  shows, the lowest region  23  is arranged in the front section  32  of the fuel tank  7  which faces away from the back carrier plate  15  and the operator  14 . 
     All sections of the tank base  8  are downwardly inclined toward the lowest region  23  resulting in the tank base  8  having a funnel-like shape. In this way, a comparatively high fill level can be achieved in the fuel tank  7  with a very small amount of fuel. Accordingly, residual amounts of fuel in the fuel tank  7  can be easily drawn therefrom. The lowest region  23  is thereby advantageously configured as small as possible. However, the lowest region  23  is shaped such that the suction head  18  is accommodated in the lowest region  23 . 
       FIG. 7  shows an embodiment for the configuration of the fuel tank  7 . The same reference symbols identify the corresponding elements from the previous figures. The fuel tank  7  has a tank base  28  having a first inclined section  29 . The section  29  extends from a side wall  25  of the fuel tank  7  over a large part of the width (d) of the tank base  28  up to the lowest region  23 . The lowest region  23  borders on the opposite-lying wall  24  of the fuel tank  7 . The section  29  is inclined thereby at an angle α, which is between about 7° and about 30° and advantageously between about 10° and about 20°, relative to the horizontal line H. The lowest region  23  has a width (i), which is advantageously less than 20% of the width (d) of the tank base  28 . The section  29  has a width (j), which advantageously is at least 70% of the width (d) of the tank base  28 , especially at least 90% of the width (d) of the tank base  28 . 
     As  FIG. 7  shows, the lowest region  23 , in which the suction head  18  is also disposed, is arranged at the side of the fuel tank  7 , which is arranged adjacent to the blower outlet of the blower and adjacent to the right arm of the operator  14 . The lowest region  23  is thereby arranged on the side of the blower on which also the blower tube  12  is guided and on which the handle  13 , with which the operator  14  guides the blower tube  12 , is arranged. In the embodiment the operator guides the blower  1  with the right hand  26  ( FIG. 1 ). If the back carrier  2  is carried with only one shoulder strap ( 3 ,  4 ), then the configuration shown in  FIG. 4 , in which the left shoulder strap  4  is arranged on the left shoulder of the operator  14  and the right shoulder strap  3  is not arranged on a shoulder, is typical. In this configuration the right side of the blower  1  and thus also the fuel tank  7  tilt downward. For this reason, the lowest region  23  should be arranged on this side of the blower  1 , in this example the right side, when viewing the back of the operator  14 . 
     It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.