The present disclosure is related to an auger. More specifically, the disclosure is related to an earth auger for making a hole in a ground.

Earth augers have been used for example by farmers since the 19 ^th century to drill holes for posts in the ground. An earth auger is also known as a post-hole auger or earth drill.

The most common design of earth auger comprises a helical screw blade winding around a lower portion of a rod or shaft. In operation a lower edge of the helical screw blade scrapes soil at the bottom of the hole, and the rest of the helical screw blade acts like a screw conveyor to lift loosened soil upwards from the bottom of the hole. When a desired depth of the hole is reached, the earth augers is withdrawn or pulled out of the hole and most of the soil being in the screw blade portion of the earth auger is scooped out of the hole. Nowadays, earth augers are typically configured for being operated by a motor being operatively connected an upper end portion of the rod. Depending i.a. on the type of soil and the diameter of the helical screw blade, the earth auger may require a relatively powerful and "tailormade" motor which tends to be heavy. A heavy motor, typically 10- 15 kg, may be strenuous to move between their operating positions, especially over a certain period of time which is typically the situation for a farmer or other persons using it in its profession. On the other hand, a relatively heavy motor may facilitate downward movement of the earth auger since the weight will urge the lower edge of the helical screw blade into the soil of the bottom of the hole. Such a motor typically comprises a combustion engine. A combustion engine negatively affects the environment and may represent a health risk for an operator that may be exposed to exhaust gas from the engine. Publication WO 2019/169180 Al discloses a screw pile system comprising one or more hollow pile shaft extensions, a grouting module comprising a flange to create an annular space in a substrate around the one or more shaft extensions, and configured to direct flow of grout out of the module to fill the annular space. The screw pile system further comprises a screw pile lead extension having auger flights disposed thereon for advancing the pile into the substrate. A most distal of the one or more hollow pile shaft extensions is connected to an upper surface of the grouting module, and the lead extension is connected to a lower surface of the grouting module.

Publication US2013101360 Al discloses a helical screw pile includes a longitudinal shaft having a top end and a bottom end with a plurality of helical plates arranged on the shaft in increasing diameter from the top to the bottom.

Publication US6502649 Bl discloses an auger for drilling fishing holes in ice on a body of water has an elongated shank supporting a continuous helical flight and a plurality of partially helical scoop-like members having leading radial edges.

Publication CN110510847 A discloses a cutting auger comprising a central shaft and spiral blades, wherein the spiral blades are arranged on the surface of the central shaft.

Another type of earth auger is configured with two vertical blades instead of a helical screw. Instead of scraping the soil at the bottom of the hole, the vertical blade type earth auger cuts a cylindrical plug out of the soil which is then held by friction or cohesion between the two blades. The vertical blade type earth auger is suitable only for certain types of soil and must be pulled out of the hole for emptying the soil cylinder. An advantage of the vertical blade type earth auger is that it for a similar type of soil normally requires less force to be rotated as compared with the helical screw blade type earth auger.

There is a need for an earth auger that is suitable for a great range of soil types, while at the same time requires less torque to be operated as compared with the common helical screw blade type earth auger.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow.

The inventor has through extensive trial and testing arrived at an earth auger configured for being driven by a battery-operated driving means, such as a standard drill commercially available for consumers.

The invention is defined by the independent patent claim. The dependent claims define advantageous embodiments of the invention.

In what follows when discussing two neighbouring helix elements, the helix element being closest to the first end portion of the rod will be denoted lower helix element, and the helix element of two neighbouring helix elements being closest to the second end portion of the rod will be denoted upper helix element.

In an aspect of the invention, there is provided an earth auger for providing a hole in a ground, the earth auger comprising:

- a rod having a first end portion and a second end portion;

- at least two helix elements secured axially spaced apart to the rod, wherein each of the helix elements having a first end face extending from a perimeter face of the helix element, and a second end face extending from a perimeter face of the helix element, and a gap extending between an outer end portion of the first end face and an outer end portion the second end face. A minimum distance between to neighbouring helix elements is less than the gap of the helix elements of the neighbouring helix elements being closest to the first end portion of the rod.

The minimum distance is the distance between the outer end portion of the second end face of the lower helix element of two neighbouring elements, and the outer end portion of the first end face of the neighbouring upper helix element.

Securing the helix elements to the rod so that a minimum distance between to neighbouring helix elements is less than a gap of the helix elements of the neighbouring helix elements being closest to the first end portion of the rod, i.e., the lower helix element, has during tests proved to be very effective in bringing the soil upwards from the bottom of a hole provided by the earth auger. The reason for this is probably that, during rotation of the earth auger, a soil being cut by the first end face of a lower helix element is lifted along an upper surface of the lower helix element until it leaves the second end face of the lower helix element. Depending on a penetration rate of the earth auger, a portion of the soil leaving the second end face of the lower helix element will be carried by the upper auger and lifted upwards to any further helix elements. However, some of the soil leaving the second end face of the lower helix element, will be subject to the first end face of the upper helix element. Thus, during rotation of the earth auger, a portion of the soil will be subject to repeated cutting. This repeated cutting has the effect of loosening or "whirling" the soil which facilitates in bringing the soil upwards with less power as compared with common earth augers provided with a helical screw blade winding around a lower portion of a rod or shaft. Further, when being in contact with the soil, the first end face of each helix element will actively contribute to urging the earth auger downwards.

Thus, during operation of the earth auger according to the invention, the first end face of each helix element functions as a leading or cutting edge, while the second end face functions as a trailing or discharge portion.

The leading edge of at least the helix element being closest to the first end portion of the rod, may be provided with a sharp edge to facilitate cutting through the soil. A sharp edge may be particularly useful when cutting through for example frozen ground or ice. The sharp edge may be provided by the helix element itself, or by means of a separate knifelike element secured to the leading edge. Preferably, such a separate knife-like element is releasably secured to the leading edge. An advantage of a releasably secured knife-like element is that it can be replaced when worn-out.

Each of the at least two helix elements are typically made from a disc having a diameter, wherein a distance between a center portion of two neighbouring helix elements may be less than a diameter of the helix element of the two neighbouring helix elements being closest to the first end portion of the rod. A center portion may typically be the portion of the disc providing the connection with the rod. The connection is typically made by a weld, but a locked thread connection is also conceivable. Providing a distance between a center portion of two neighbouring helix elements being less than a diameter of the helix element of the two neighbouring helix elements being closest to the first end portion of the rod, is advantageous with respect to bringing the soil upwards while the earth auger is rotated.

In one embodiment of the invention is the helix element being closest to the first end portion of the rod has a diameter being smaller than a diameter of a helix element being closer to the second end portion of the rod. This has the effect that the hole in the ground is provided in a number of steps. The number of steps is determined by the number of increments of diameter of the helix elements. Such a stepwise creation of a hole may be of particular interest when the helix element being closest to the second end portion is relatively large, and/or if the soil is heavy, sticky, or relatively solid and compact.

For an earth auger to be rotated by a battery drill as mentioned above, helix element having a diameter of for example 120 mm may be considered at relatively large. However, the earth auger may be rotated also by more powerful motors, for example combustion motors or hydraulic motors. For such motors the earth auger may be provided with larger helix elements having a diameter being larger than for example 120 mm.

The earth auger according to the invention may be provided with more than two helix elements. In one embodiment increases a diameter of the helix elements linearly between the helix element being closest to the first end portion of the rod, and the helix element being closest to the second end portion of the rod. At least a bottom portion of a hole provided with such an earth auger may have a conical or frustoconical shape. In an alternative embodiment increases a diameter of the helix elements non-linearly between the helix element being closest to the first end portion of the rod, and the helix element being closest to the second end portion of the rod. At least a bottom portion of a hole made by an earth auger having such a configuration may have a stepwise decreasing diameter. The perimeter face of at least one of the helix elements may be provided with at least one indentation. Tests have surprisingly shown that the indentations have a positive effect in reducing resistance against rotation. The positive effect is greater the harder the soil in which the hole is provided. The effect is probably due to the rasping effect provided by the indentations. To provide an even further reduced resistance against rotation at least a portion of the perimeter face of at least one of the helix elements may be provided with serrations. Such serrations provide a "saw-blade" effect which at least for some soils results in a relatively smooth surface or wall of the hole. In one embodiment is the perimeter face of the helix element provided with a combination of indentations and serrations.

At least one of the at least two helix elements may be provided with lip or protrusion extending upwardly from a perimeter portion of a top surface of the helix element. Such a lip has proven to be effective in facilitating bringing or "shuffling" loosened soil upwards in a hole being provided by the earth auger according to the invention, especially when the soil in the ground is relatively loose.

The helix elements may have a constant pitch angle between the first end face and the second end face. However, in an alternative embodiment the helix elements may have a variable pitch between the first end face and the second end face. In one embodiment is a portion of at least one helix element provided with a flat portion, i.e. a portion between the first end face and the second end face being perpendicular to a longitudinal axis of the rod. In still another embodiment is a helix element provided with a negative pitch angle. Tests have indicated that said flat portion and/or said negative pitch angle may be preferred for earth augers to be used for making holes in solid, hard gritty soil, especially in embodiments wherein the perimeter of the helix element is provided with indentations and/or serrations. When rotated, a helix element provided with an uneven (not constant) pitch angle may resemble a longitudinal "oscillating" or scraping effect towards the soil of the borehole.

In an embodiment of the invention wherein the earth auger is provided with helix elements of different diameters, a pitch angle of the helix elements may decrease with in- creasing diameter of the helix elements. An effect of this is that a difference of an earth removing effect or "aggressiveness" between helix elements of different diameters is reduced.

Preferably, the gaps of the helix elements may be oriented in a spiral manner along the longitudinal axis of the rod. This has the effect of effectively transferring loosened soil upwards from the lowermost helix element. At least a portion of the loosened soil discharged from the second end face of a lower helix element is effectively transferred to or "grabbed" by the first end face of a neighbouring helix element being above said lower helix element. Tests have shown that without arranging the gaps in such a spiral manner along the rod, a considerably smaller portion of loosened soil discharged from the second end face of a lower helix element is "grabbed" by the first end face of a neighbouring helix element. Thus, arranging the gaps in a spiral manner along the rod may result in a less effective earth auger.

The first end portion of the rod may be provided with a blunted tip. A blunted tip may have the effect of guiding the earth auger past obstructions like stones that the tip may abut against during operation.

Especially when used in solid, hard ground, it may be advantageous to provide the first end portion of the rod is provided with a cutting element. Such a cutting element may have a conical shape, for example. Alternatively the cutting element may be a drill bit configured for providing a rasping effect on the soil.

In the following is described examples of embodiments illustrated in the accompanying drawings, wherein:

Fig. la shows a perspective view of a first embodiment of the earth auger according to the invention;

Fig. lb shows in larger scale a detail of a lower portion of the earth auger shown in fig. la, wherein a lowermost helix element is further provided with a knifelike element; Fig. 2a shows a perspective view of a second embodiment of the earth auger according to the invention;

Fig. 2b shows in larger scale a detail of a lower portion of the earth auger shown in fig. 2a; and

Fig. 2c shows in larger scale a portion of helix elements.

Any positional indications refer to the position shown in the figures.

In the figures, same or corresponding elements are indicated by same reference numerals. For clarity reasons, some elements may in some of the figures be with-out reference numerals.

A person skilled in the art will understand that the figures are just principal drawings. The relative proportions of individual elements may also be distorted.

In the figures, reference numeral 1 denotes an earth auger according to the invention.

The earth auger 1 comprises a rod 3 having a first end portion 5 and a second end portion 7 opposite the first end portion 5. In a position of use, the first end portion 5 is the lowermost portion of the earth auger 1.

The earth auger 1 comprises helix elements 10 secured axially spaced apart to the rod 3. The helix elements 10 are typically made from circular discs provided with a central aperture and a split extending from a perimeter to the central aperture. The helix elements 10 are in the shown embodiments secured to the rod 3 by welding a perimeter of the central aperture to the rod 3. Preferably, the helix elements 10 are formed prior to being secured to the rod 3. However, the elements 10 may alternatively be formed in a helix after being secured to the rod 3.

In figures la and lb, the earth auger 1 comprises four helix elements 10 made from discs having the same diameter. Thus, a perimeter of the helix elements 10 is parallel with a central axis of the rod 3. The first end portion 5 of the rod 3 is provided with a blunted tip 5'. In the embodiment shown is the blunted tip 5' provided with a helix groove 5" configured for providing a certain drilling effect when the earth auger 1 is rotated. The second end portion 7 of the rod 3 is provided with a hexagonal portion to be gripped by a chuck of a standard handheld drill, such as a battery-operated drill (not shown).

Each of the helix elements 10 shown in figures la and lb are provided with five indentations 11 (three shown) spaces apart in a perimeter portion of the helix elements 10.

Each helix element 10 has a first end face 12 and a second end face 14. Each first end face 12 and second end face 14 of the helix elements 10 extend from a perimeter of the helix element 10 to the surface of the rod 3 to which the helix element 10 is secured. A gap 16 extends between an outer end portion 12' of the first end face 12 and an outer end portion 14' of the second end face 14.

In fig. lb, the helix element 10 being closest to the first end portion 5 of the rod 3, is provided with a knife-like element 13 that encloses the first end face 12. The knife-like element 13 is releasable secured to the helix element 10 by means of countersunk bolts (two shown).

A minimum distance 18 between to neighbouring helix elements 10 is less than a gap 16 of the helix element 10 of the neighbouring helix elements 10 being closest to the first end portion 5 of the rod 3. The minimum distance is in fig. lb the distance 18 between the outer end portion 14' of the second end face 14 of the lower helix element 10 of two neighbouring elements, and the outer end portion 12' of the first end face 12 of the neighbouring upper helix element 10.

Turning now to figures 2a - 2c showing an alternative embodiment of the earth auger 1 according to the invention. The earth auger 1 comprises six helix elements 10, some of which have different diameters. The helix element 10 being closest to the first end portion 5 of the rod 3 has a diameter being smaller than a diameter of the next helix element 10 being closer to the second end portion 7 of the rod 3. Helix element 10 number two from the first end portion 5 of the rod 3 has a diameter being smaller than a diameter of the next helix elements 10 (helix elements number three to six). Helix elements number three and four from the first end portion 5 have are made from discs having the same dimensions. The two uppermost helix elements 10 are the largest helix elements 10 and have the same dimensions.

A pitch of the helix element 10 being closest to the first end portion 5 of the rod 3 (the lowermost helix element 10) has a greater pitch angle than the succeeding helix elements 10. Thus, the lowermost helix element 10 has the greatest gap 16 with respect to its diameter. In the second embodiment shown in figures 2a and 2b, the relationship between the gap 16 and the diameter of the helix elements 10 decreases with increasing diameter of the helix elements 10, i.e., an average pitch angle between the first end face 12 and the second end face 14 decreases with increasing diameter of the helix elements 10.

As best seen in fig. 2b, the split portions forming the gaps 16 of the helix elements 10 are oriented in a spiral manner along the longitudinal portion of the rod 3, i.e., an imaginary line passing through the gaps 16 at a surface of the rod 3 is spiralled about 180° between the lowermost, smallest helix element 10 and the uppermost, largest helix element. The embodiment of the earth auger 1 shown in figures la and lb has a similar configuration with respect to the orientation of the gaps 16 with respect to the rod 3.

Fig. 2c shows in a larger scale a detail of the two uppermost helix elements 10 of the second embodiment of the invention. The perimeter face of the helix elements 10 shown are provided with indentations 11 (only some shown) to provide a rasping effect against the soil when the earth auger 1 rotated. The perimeter face of the two uppermost helix elements 10 shown in fig. 2c are further provided with serrations 11' between the indentations 11 in the perimeter face.

As best seen in fig. 2b, the first end portion 5 of the rod 3 is provided with a cutting element 6 configured for cutting or milling the ground to loosen a portion of the soil before the soil is "grabbed" by the lowermost and the subsequent helix elements 10.

To enhance a "shuffle" effect of the helix element 10, a side portion of one or more of the helix elements may be provided with an upwardly protruding lip or wall portion (not shown), so that the one or more helix elements 10 provided with such a lip, forms a bowl".

One or more of the helix elements 10 shown in figures 2a and 2b may be provided with a sharp edge (not shown), for example a knife-like element 13 as shown in fig. lb and discussed above.

From the above it should be clear that the earth auger 1 according to the invention is provided with at least two helix elements 10, each of which has a first end face 12 providing a soil leading or cutting edge. In contrast to a prior art earth auger that comprises a helical, continuous screw blade winding around a rod, and thus has only one "cutting edge" provided by the lower end portion of the screw blade, the earth auger 1 according to the invention has proven to be more effective in cutting into the soil while it at the same time requires less power to be rotated. Less power makes possible rotating the earth auger 1 by lighter equipment, such as for example a battery powered electrical drill.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.