GB2106762A

GB2106762A - A resilient harrow tine

Info

Publication number: GB2106762A
Application number: GB08227150A
Authority: GB
Inventors: Larsen; Kim Ilberg Christensen
Original assignee: Kongskilde Koncernselskab AS
Current assignee: Kongskilde Koncernselskab AS
Priority date: 1982-09-23
Filing date: 1982-09-23
Publication date: 1983-04-20
Also published as: GB2106762B

Abstract

In a resilient harrow tine of S-like shape and comprising a resilient hoop portion bent substantially to form a circle and having a cross-section the basic form of which is a rectangle with a ratio between the width and the height of approximately 3, the ratio between the strength and the material consumption has been optimized by designing the cross-section (4) so that the neutral stress line (6) is displaced in the direction towards the outwardly facing long side (5) of the cross-section of the resilient hoop portion in relation to the longitudinal centre line (7) of the circumscribed rectangle (8) of the cross- section. <IMAGE>

Description

SPECIFICATION A resilient harrow tine The invention relates to a resilient harrow tine of S-like shape and comprising an upper, resilient hoop portion bent substantially to form a circle and having a cross-section, the circumscribed rectangle of which has a ratio between the width and the height of about 3, the cross-sectional long side facing outwards in the resilient hoop portion being substantially rectilinear.

A harrow tine of said type is generally produced from a rolled steel bar of rectangular or substantially rectangular cross-section.

Such a harrow tine blank is disclosed in the following patent specifications: Danish No. 111,044, UK No. 1,178,370, German No. 1,757,146, and French No. 1,565,170, according to which the cross-section is slightly convex at one of its long sides. By bending said blank into S-shape the cross-section assumes a practically symmetrical shape and the neutral axis of stress becomes consequently coincident with the longitudinal centre line of the cross-section.

When in operation, the resilient hoop portion of the tine is tensioned at its outwardly facing side and for this reason much care is taken in dimensioning and production to avoiding stress concentrations at this side. In known harrow tines this is achieved, inter alia by providing suitably smooth transitions between the outwardly facing side and the short sides and by ball hammering the surfaces whether the cross-section of the blank is absolutely rectangular or possibly slightly curved as stated above.

As a consequence ofthe above mentioned measures, harrow tines manufactured according to the priortechnique may fulfil the conditions necessary for the working ability of the tine with a view to strength, resilience and stability.

By thorough analysis of the stress to which the harrow tine is subjected when in operation, for instance by means of strain gauges and by estimating the stress distribution over the cross-section, it has been established, however, that the material is not fully utilized. This implies that known harrow tines require more material than strictly necessary to obtain the desired strength, and from this recognition it is an aim of the invention to provide a harrow tine with an optimum proportion between strength and material consumption.

The harrow tine according to the invention is characterized in that the opposed cross-sectional long side, i.e. the inwardly facing side of the resilient hoop portion, includes portions that are retracted so from the corresponding long side of the circumscribed rectangle that the neutral stress line of the cross-section is displaced from the longitudinal centre line of the circumscribed rectangle towards the long side facing outwards in the resilient hoop portion.

Such a displacement of the neutral line entails a reduction in tensile stress, particularly at the corner areas at the outwardly facing long side as compared to the tensile stress in the corresponding areas of prior harrow tines. The displacement of the line further causes the compressive stress to intensify in the cross-sectional portions facing inwardly, but in view of the fact that the resilient tine material is less notch-sensitive to compressive stress than to tensile stress, the altered stress distribution obtained may be utilized to reduce the cross-sectional area without influencing the lifetime of the harrow tine measured in the number of influences or pulses within a given range of load.

These features provide for obtaining savings in weight from about 5 to 25% in comparison with corresponding prior art S-shaped harrow tines.

The invention is illustrated in the accompanying drawings, in which Figure 1 shows a side elevation of an S-shaped harrow tine, Figure 2 is a cross-section on a larger scale along line I-I in Figure 1 and in a first embodiment of the invention, and Figure 3 is a similar cross-section of another embodiment.

The harrow tine shown in Figure 1 comprises in the usual manner a rectilinear attachment portion 1 continuing into a resilient hoop portion 2 bent substantially along a circle and passing into an opposedly curved portion 3 forming the harrow tine proper and to which a separate harrow point or tip, not shown, may be secured. According to Figure 2 the harrow tine has a cross-section 4 with a basic form like a symmetrical trapezium, the base line 5 of which faces upwards, i.e. outwardly in the resilient hoop portion 2.

The neutral stress line 6 of said cross-section is located nearer to the base line 5 than the longitudinal centre line 7 of the circumscribed reactangle 8 of the cross-section. The same strength may thus be obtained with a cross-sectional area that is reduced approximately 15% in comparison with a harrow tine of ordinary design.

Figure 3 shows another embodiment in which the cross-section 9 of the harrow tine in its basic form is a rectangle, preferably with circular-arched short sides 10. The inwardly facing cross-sectional side 11 of the resilient hoop portion 2 presents asymmetric- al trapezoidal recess 12 with a width declining inwardly of the cross-section.

The neutral stress line 13 of said cross-section is displaced towards the outwardly facing long side 14 of the cross-section in relation to the longitudinal centre line 15 of the circumscribed rectangle 16 of the cross-section.

The reduction in area is in casu approximately 20% in comparison with harrow tines of ordinary design.

1. A resilient harrow tine of S-iike shape and comprising an upper, resilient hoop portion bent substantially to form a circle and having across- section, the circumscribed rectangle of which has a ratio between the width and the height of about 3, the cross-sectional long side facing outwards in the resilient hoop portion being substantially rectilinear, characterized in that the opposed cross-sectional long side includes portions that are retracted so from

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A resilient harrow tine The invention relates to a resilient harrow tine of S-like shape and comprising an upper, resilient hoop portion bent substantially to form a circle and having a cross-section, the circumscribed rectangle of which has a ratio between the width and the height of about 3, the cross-sectional long side facing outwards in the resilient hoop portion being substantially rectilinear. A harrow tine of said type is generally produced from a rolled steel bar of rectangular or substantially rectangular cross-section. Such a harrow tine blank is disclosed in the following patent specifications: Danish No. 111,044, UK No. 1,178,370, German No. 1,757,146, and French No. 1,565,170, according to which the cross-section is slightly convex at one of its long sides. By bending said blank into S-shape the cross-section assumes a practically symmetrical shape and the neutral axis of stress becomes consequently coincident with the longitudinal centre line of the cross-section. When in operation, the resilient hoop portion of the tine is tensioned at its outwardly facing side and for this reason much care is taken in dimensioning and production to avoiding stress concentrations at this side. In known harrow tines this is achieved, inter alia by providing suitably smooth transitions between the outwardly facing side and the short sides and by ball hammering the surfaces whether the cross-section of the blank is absolutely rectangular or possibly slightly curved as stated above. As a consequence ofthe above mentioned measures, harrow tines manufactured according to the priortechnique may fulfil the conditions necessary for the working ability of the tine with a view to strength, resilience and stability. By thorough analysis of the stress to which the harrow tine is subjected when in operation, for instance by means of strain gauges and by estimating the stress distribution over the cross-section, it has been established, however, that the material is not fully utilized. This implies that known harrow tines require more material than strictly necessary to obtain the desired strength, and from this recognition it is an aim of the invention to provide a harrow tine with an optimum proportion between strength and material consumption. The harrow tine according to the invention is characterized in that the opposed cross-sectional long side, i.e. the inwardly facing side of the resilient hoop portion, includes portions that are retracted so from the corresponding long side of the circumscribed rectangle that the neutral stress line of the cross-section is displaced from the longitudinal centre line of the circumscribed rectangle towards the long side facing outwards in the resilient hoop portion. Such a displacement of the neutral line entails a reduction in tensile stress, particularly at the corner areas at the outwardly facing long side as compared to the tensile stress in the corresponding areas of prior harrow tines. The displacement of the line further causes the compressive stress to intensify in the cross-sectional portions facing inwardly, but in view of the fact that the resilient tine material is less notch-sensitive to compressive stress than to tensile stress, the altered stress distribution obtained may be utilized to reduce the cross-sectional area without influencing the lifetime of the harrow tine measured in the number of influences or pulses within a given range of load. These features provide for obtaining savings in weight from about 5 to 25% in comparison with corresponding prior art S-shaped harrow tines. The invention is illustrated in the accompanying drawings, in which Figure 1 shows a side elevation of an S-shaped harrow tine, Figure 2 is a cross-section on a larger scale along line I-I in Figure 1 and in a first embodiment of the invention, and Figure 3 is a similar cross-section of another embodiment. The harrow tine shown in Figure 1 comprises in the usual manner a rectilinear attachment portion 1 continuing into a resilient hoop portion 2 bent substantially along a circle and passing into an opposedly curved portion 3 forming the harrow tine proper and to which a separate harrow point or tip, not shown, may be secured. According to Figure 2 the harrow tine has a cross-section 4 with a basic form like a symmetrical trapezium, the base line 5 of which faces upwards, i.e. outwardly in the resilient hoop portion 2. The neutral stress line 6 of said cross-section is located nearer to the base line 5 than the longitudinal centre line 7 of the circumscribed reactangle 8 of the cross-section. The same strength may thus be obtained with a cross-sectional area that is reduced approximately 15% in comparison with a harrow tine of ordinary design. Figure 3 shows another embodiment in which the cross-section 9 of the harrow tine in its basic form is a rectangle, preferably with circular-arched short sides 10. The inwardly facing cross-sectional side 11 of the resilient hoop portion 2 presents asymmetric- al trapezoidal recess 12 with a width declining inwardly of the cross-section. The neutral stress line 13 of said cross-section is displaced towards the outwardly facing long side 14 of the cross-section in relation to the longitudinal centre line 15 of the circumscribed rectangle 16 of the cross-section. The reduction in area is in casu approximately 20% in comparison with harrow tines of ordinary design. CLAIMS

1. A resilient harrow tine of S-iike shape and comprising an upper, resilient hoop portion bent substantially to form a circle and having across- section, the circumscribed rectangle of which has a ratio between the width and the height of about 3, the cross-sectional long side facing outwards in the resilient hoop portion being substantially rectilinear, characterized in that the opposed cross-sectional long side includes portions that are retracted so from the corresponding long side of the circumscribed rectangle that the neutral stress line of the crosssection is displaced from the longitudinal centre line of the circumscribed rectangle towards the long side facing outwards in the resilient hoop portion.

2. A harrow tine according to claim 1, characterized in that the basic form of the cross-section is a symmetrical trapezium the base line of which faces outwards in the resilient hoop portion.

3. A harrow tine according to claim 1 and wherein the basic form of the cross-section is a rectangle, preferably with circular-arched short sides, characterized in that the cross-sectional side facing inwardly in the resilient hoop portion has a symmetrical recess with a width declining inwardly of the cross-section.

4. A harrow tine according to claim 3, characterized in that the recess is trapezoidal.

5. A harrow tine substantially as described herein with reference to and as illustrated in Figure 1 and Figure 2 or 3 of the accompanying drawings.

6. A harrow including tines according to any preceding claim.