Blade apparatus and its control method in bulldozer

Claim 5

An apparatus in accordance with claim 2, wherein said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade in the range of about 5° to about 20° with respect to said digging posture of said blade in order to perform earth-moving work and are able to control said blade at a forwardly inclined angle of said blade in the range of about 5° to about 45° with respect to said digging posture of said blade in order to perform earth-dumping work, wherein said at least one hydraulic pump comprises at least one main hydraulic pump for supplying said hydraulic fluid to said first and second hydraulic cylinders, and at least one assistant hydraulic pump for assisting said at least one main hydraulic pump in supplying said hydraulic fluid to said first and second hydraulic cylinders, and wherein said hydraulic drive system includes at least one assistant solenoid selector valve which is controllable by an external signal, each said assistant hydraulic pump being connectable through a respective assistant solenoid selector valve to a delivery line from a respective one of said at least one main hydraulic pump to said first and second hydraulic cylinders.

Claim 6

An apparatus in accordance with claim 2, wherein said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade in the range of about 5° to about 20° with respect to said digging posture of said blade in order to perform earth-moving work and are able to control said blade at a forwardly inclined angle of said blade in the range of about 5° to about 45° with respect to said digging posture of said blade in order to perform earth-dumping work, wherein said at least one hydraulic pump of said hydraulic drive system comprises at least one variable displacement hydraulic pump for supplying a hydraulic fluid to said hydraulic cylinders, said at least one variable displacement hydraulic pump being controllable by an external signal.

Claim 7

An apparatus in accordance with claim 2, wherein said at least one hydraulic pump comprises at least one fixed displacement hydraulic pump, wherein said hydraulic drive system further comprises a plurality of solenoid selector valves, and wherein a delivery line of said at least one fixed displacement hydraulic pump is connectable to a bottom-side line of said first hydraulic cylinder, a head-side line of said first hydraulic cylinder is connectable to a bottom-side line of said second hydraulic cylinder through one of said plurality of solenoid selector valves, and a head-side line of said second hydraulic cylinder is connectable to a drain line through another one of said plurality of solenoid selector valves, thereby making up a series circuit, whereby said first hydraulic cylinder and said second hydraulic cylinder are able to control said blade at a rearwardly inclined angle of said blade in the range of about 5° to about 20 with respect to said digging posture of said blade in order to perform earth-moving work and to control said blade at a forwardly inclined angle of said blade in the range of about 5° to about 45° with respect to said digging posture of said blade in order to perform earth-dumping work.

Claim 8

An apparatus in accordance with claim 2, wherein said blade comprises a concave front panel and a blade edge member attached to a lower end of said concave front panel such that a line tangential to said lower end of said concave front panel is inclined rearwardly with respect to a front surface of said blade edge member.

Claim 9

An apparatus in accordance with claim 6, wherein said line tangential to said lower end of said concave front panel is inclined rearwardly with respect to said front surface of said blade edge member at an angle which is greater than zero and less than or equal to about 15°.

Claim 12

An apparatus in accordance with claim 8, wherein said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade in the range of 5° to 20° with respect to said digging posture of said blade in order to perform earth-moving work, and to control said blade at a forwardly inclined angle of said blade in the range of 5° to 45° with respect to said digging posture of said blade in order to perform earth-dumping work, wherein said at least one hydraulic pump comprises at least one main hydraulic pump for supplying said hydraulic fluid to said first and second hydraulic cylinders and at least one assistant hydraulic pump for assisting said at least one main hydraulic pump in supplying said hydraulic fluid to said first and second cylinders, wherein said hydraulic drive system includes at least one assistant solenoid selector valve controlled by an external signal, each said assistant hydraulic pump being connectable to a delivery line of one of said at least one main hydraulic pump through a respective one of said at least one assistant solenoid selector valve.

Claim 13

An apparatus in accordance with claim 8, wherein said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade in the range of 5° to 20° with respect to said digging posture of said blade in order to perform earth-moving work, and to control said blade at a forwardly inclined angle of said blade in the range of 5° to 45° with respect to said digging posture of said blade in order to perform earth-dumping work, and wherein said at least one hydraulic pump of said hydraulic drive system comprises at least one variable displacement hydraulic pump for supplying hydraulic fluid to said first and second hydraulic cylinders, said at least one variable displacement hydraulic pump being controlled by an external signal.

Claim 14

An apparatus in accordance with claim 8, wherein said at least one hydraulic pump comprises at least one fixed displacement hydraulic pump, wherein said hydraulic drive system includes a plurality of solenoid selector valves, and wherein a delivery line of one of said at least one fixed displacement hydraulics pump is connectable to a bottom-side line of said first hydraulic cylinder, a head-side line of said first hydraulic cylinder is connectable to a bottom-side line of said second hydraulic cylinder through one of said plurality of solenoid selector valves, a head-side line of said second hydraulic cylinder is connectable to a drain line through another one of said plurality of solenoid selector valves, thereby making up a series circuit, whereby said first hydraulic cylinder and said second hydraulic cylinder are able to control said blade at a rearwardly inclined angle of said blade in the range of 5° to 20° with respect to said digging posture of said blade in order to perform earth-moving work and to control said blade at a forwardly inclined angle of said blade in the range of 5° to 45° with respect to said digging posture of said blade in order to perform earth-dumping work.

Claim 15

An apparatus in accordance with claim 8, wherein said blade comprises a concave front panel and a blade edge member attached to a lower end of said concave front panel such that a line tangential to said lower end of said concave front panel is inclined rearwardly with respect to a front surface of said blade edge member.

Claim 16

An apparatus in accordance with claim 12, wherein said line tangential to said lower end of said concave front panel is inclined rearwardly with respect to said front surface of said blade edge member at an angle which is greater than zero and less than or equal to about 15°.

Claim 19

An apparatus in accordance with claim 14, wherein said third acute angle is greater than zero and less than or equal to about 15°.

Claim 20

An apparatus in accordance with claim 14, wherein said third acute angle is in the range of about 10° to about 15°.

Claim 25

A method in accordance with claim 18, wherein the thus formed predetermined rearwardly inclined angle is in the range of about 10° to about 20°.

Claim 28

A method in accordance with claim 20, wherein the thus formed predetermined forwardly inclined angle is in the range of about 10° to about 45°.

Claim 29

A method in accordance with claim 20, further comprising: performing earth-moving work by inclining said blade rearwardly by a predetermined angle with respect to said digging posture of said blade in order to provide an earth-moving posture of said blade for performing earth-moving which is inclined more rearwardly than said digging posture of said blade, the thus formed predetermined rearwardly inclined angle being in the range of about 5° to about 20°, thereby increasing the amount of earth carried by said blade during earth-moving work.

Claim 30

A method in accordance with claim 22, wherein the thus formed predetermined forwardly inclined angle is in the range of about 10° to about 45°, and the thus formed predetermined rearwardly inclined angle is in the range of about 10° to about 20°.

Claim 31

A method in accordance with claim 22, wherein said bulldozer body is provided with a tilt/pitch changeover means for controlling said blade to incline said blade forwardly or rearwardly, a pitch speed changeover means, and a control means for raising and lowering said blade, said method further comprising: selecting a desired one of a posture for digging work, a posture for earth-moving work, and a posture for earth-dumping work by operating said tilt/pitch changeover means, said pitch speed changeover means, and said control means.

Claim 32

A method in accordance with claim 22, wherein said bulldozer body is provided with a pitch-dump selector means for controlling said blade to incline said blade forwardly or rearwardly, a pitch-back selector means, and a control means for raising and lowering said blade, said method further comprising: selecting a desired one of a posture for digging work, a posture for earth-moving work, and a posture for earth-dumping work by operating said pitch-dump selector means, said pitch-back selector means, and said control means.

Claim 37

A method in accordance with claim 27, further comprising: performing earth-moving work by inclining said blade rearwardly such that an edge angle of said blade edge member with respect to a horizontal line is in the range of about 35° to about 45°, thereby increasing the amount of earth carried.

Claim 38

A method in accordance with claim 28, wherein said bulldozer is provided with a tilt/pitch changeover means for controlling said blade to incline said blade forwardly or rearwardly, a pitch speed changeover means, and a control means for raising and lowering said blade, said method further comprising: selecting a desired one of a posture for digging work, a posture for earth-moving work, and a posture for earth-dumping work by operating said tilt/pitch changeover means, said pitch speed changeover means, and said control means.

Claim 39

A method in accordance with claim 28, wherein said bulldozer is provided with a pitch-dump selector means for controlling said blade to incline said blade forwardly or rearwardly, a pitch-back selector means, and a control means for raising and lowering said blade, said method further comprising: selecting a desired one of a posture for digging work, a posture for earth-moving work, and a posture for earth-dumping work by operating said pitch-dump selector means, said pitch-back selector means, and said control means.

Claim 40

In an apparatus comprising: a bulldozer body; first and second frame members, each of said first and second frame members having a first end and a distal end, with each said first end being pivotally attached to a respective opposite side of said bulldozer body; a blade pivotally attached to the distal ends of said frame members, said blade having opposite transverse ends and a digging posture for performing digging work; first and second hydraulic cylinders, each of said first and second hydraulic cylinders pivotally coupling between a respective transverse end of said blade and an intermediate portion of a respective one of said first and second frame members; and a hydraulic drive system for said first and second hydraulic cylinders, said hydraulic drive system comprising at least one hydraulic pump for supplying a hydraulic fluid to said first and second hydraulic cylinders, directional control valves for controlling the supplying of the hydraulic fluid from said at least one hydraulic pump to said first and second hydraulic cylinders, whereby said first and second hydraulic cylinders can be extended or contracted by said hydraulic drive system so that said blade can be inclined forwardly or rearwardly; the improvement comprising each of said first and second hydraulic cylinders having a length such that said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade in the range of about 5° to about 20° with respect to said digging posture of said blade in order to provide an earth-moving posture of said blade for performing earth-moving which is inclined more rearwardly than said digging posture of said blade for performing digging work.

Claim 41

In an apparatus comprising: a bulldozer body; first and second frame members, each of said first and second frame members having a first end and a distal end, with each said first end being pivotally attached to a respective opposite side of said bulldozer body; a blade pivotally attached to the distal ends of said frame members, said blade having opposite transverse ends and a digging posture for performing digging work; first and second hydraulic cylinders, each of said first and second hydraulic cylinders pivotally coupling between a respective transverse end of said blade and an intermediate portion of a respective one of said first and second frame members; and a hydraulic drive system for said first and second hydraulic cylinders, said hydraulic drive system comprising at least one hydraulic pump for supplying a hydraulic fluid to said first and second hydraulic cylinders, directional control valves for controlling the supplying of the hydraulic fluid from said at least one hydraulic pump to said first and second hydraulic cylinders, whereby said first and second hydraulic cylinders can be extended or contracted by said hydraulic drive system so that said blade can be inclined forwardly or rearwardly; the improvement comprising each of said first and second hydraulic cylinders having a length such that said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade in the range of about 5° to about 20° with respect to said digging posture of said blade in order to provide an earth-moving posture of said blade for performing earth-moving which is inclined more rearwardly than said digging posture of said blade for performing digging work.

Claim 42

An apparatus in accordance with claim 31, wherein each of said first and second hydraulic cylinders has a length such that said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade of at least about 10° with respect to said digging posture of said blade.

Claim 43

An apparatus in accordance with claim 31, wherein said blade has a blade edge member extending along a lower end of said blade, said blade edge member having a front face to form a blade edge angle between said front face of said blade edge member and a horizontal line when said blade is placed on the ground, and wherein said digging posture includes a blade edge angle of 55°± about 5°.

Claim 44

An apparatus in accordance with claim 33, wherein each of said first and second hydraulic cylinders has a length such that said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade of at least about 10° with respect to said digging posture of said blade.

Claim 45

An apparatus in accordance with claim 31, wherein said blade has a blade edge member extending along a lower end of said blade, said blade edge member having a front face to form a blade edge angle between said front face of said blade edge member and a horizontal line when said blade is placed on the ground, and wherein each of said first and second hydraulic cylinders has a length such that said first and second hydraulic cylinders are able to control said blade at a blade edge angle equal to or less than about 45°.

Claim 46

An apparatus in accordance with claim 31, wherein said blade has a concave front panel and a blade edge member attached to a lower end of said concave front panel such that an angle between a horizontal line and a line tangential to said lower end of said concave front panel is about 35° in said earth-moving posture.

Claim 47

An apparatus in accordance with claim 31, wherein said blade has a concave front panel, and a blade edge member is attached to said blade at a lower end of said concave front panel such that a line tangential to said lower end of said concave front panel is inclined rearwardly with respect to a front surface of said blade edge member.

Claim 48

An apparatus in accordance with claim 37, wherein said line tangential to said lower end of said concave front panel is inclined rearwardly with respect to said front surface of said blade edge member at an angle which is greater than zero and less than or equal to about 15°.

Claim 49

An apparatus in accordance with claim 37, wherein said line tangential to said lower end of said concave front panel is inclined rearwardly with respect to said front surface of said blade edge member at an angle which is in the range of about 10° to about 15°.

Claim 50

An apparatus in accordance with claim 31, wherein said first and second hydraulic cylinders are also able to control said blade at a forwardly inclined angle of said blade in the range of about 5° to about 45° with respect to said digging posture of said blade.

Claim 51

An apparatus in accordance with claim 40, wherein said hydraulic drive system further comprises a changeover control circuit for changing between a tilt mode and a pitch mode, wherein said at least one hydraulic pump comprises at least one main hydraulic pump for supplying said hydraulic fluid to said first and second hydraulic cylinders and at least one assistant hydraulic pump for assisting said at least one main hydraulic pump in supplying said hydraulic fluid to said first and second hydraulic cylinders, wherein said changeover control circuit includes at least one assistant solenoid selector valve and a speed changeover device, wherein each said at least one assistant hydraulic pump is selectively connectable through a respective one of said at least one assistant solenoid selector valve to a delivery line of a respective one of said at least one main hydraulic pump to thereby assist the respective main hydraulic pump in supplying hydraulic fluid to at least one of said first and second hydraulic cylinders at a delivery rate, which is greater than a delivery rate which would be provided by only the respective main hydraulic pump, to thereby operate at least one of said first and second hydraulic cylinders at a speed which is higher than a speed which would be provided by only the respective main hydraulic pump, and wherein said speed changeover device provides a signal to at least one assistant solenoid selector valve to connect the respective assistant hydraulic pump to the respective delivery line when the respective assistant hydraulic pump is to assist the respective main hydraulic pump.

Claim 52

An apparatus in accordance with claim 40, wherein said at least one hydraulic pump comprises at least one variable displacement hydraulic pump which is controlled by an external signal.

Claim 53

An apparatus in accordance with claim 40, wherein said hydraulic drive system further comprises a changeover control circuit for changing between a tilt mode and a pitch mode, wherein said at least one hydraulic pump comprises at least one fixed displacement hydraulic pump, wherein said changeover control circuit includes a plurality of solenoid selector valves, and wherein a delivery line of at least one of said at least one fixed displacement hydraulic pump is connectable through one of said directional control valves to a bottom-side line of said first hydraulic cylinder, a head-side line of said first hydraulic cylinder is connectable to a bottom-side line of said second hydraulic cylinder through one of said plurality of solenoid selector valves, and a head-side line of said second hydraulic cylinder is connectable to a drain line through another one of said plurality of solenoid selector valves and one of said directional control valves, thereby making up a series circuit.

Claim 54

In an apparatus comprising: a bulldozer body; first and second frame members, each of said first and second frame members having a first end and a distal end, with each said first end being pivotally attached to a respective opposite side of said bulldozer body; a blade pivotally attached to the distal ends of said frame members, said blade having opposite transverse ends and a traditional range of blade edge angles; first and second hydraulic cylinders, each of said first and second hydraulic cylinders pivotally coupling between a respective transverse end of said blade and an intermediate portion of a respective one of said first and second frame members; and a hydraulic drive system for said first and second hydraulic cylinders, said hydraulic drive system comprising at least one hydraulic pump for supplying a hydraulic fluid to said first and second hydraulic cylinders, directional control valves for controlling the supplying of the hydraulic fluid from said at least one hydraulic pump to said first and second hydraulic cylinders, whereby said first and second hydraulic cylinders can be extended or contracted by said hydraulic drive system so that said blade can be inclined forwardly or rearwardly, whereby in said traditional range of blade edge angles earth-moving work is performed under a condition wherein an operator controls said blade by applying a force to said blade so that said blade is pressed downwardly against a ground surface such that a front portion of the bulldozer body is apt to lift upwardly, thereby reducing a traction force of said apparatus with respect to a ground surface, the improvement comprising each of said first and second hydraulic cylinders having a length such that said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade with respect to the posture of said blade in said traditional range of blade edge angles, such that at said rearwardly inclined angle of said blade earth-moving work can be performed under a condition wherein a weight of earth loaded on said blade is sufficiently greater, than an amount of earth loaded on said blade when positioned in said traditional range, so that the greater weight of the thus loaded earth acts on said blade in such a manner as to cause said blade to bite into the ground surface so that an operator controls said blade by applying a lifting force to said blade, thereby causing said front end of said bulldozer body to be pressed downwardly against the ground surface so as provide a substantially uniform ground contact pressure.

Claim 55

In an apparatus comprising: a bulldozer body; first and second frame members, each of said first and second frame members having a first end and a distal end, with each said first end being pivotally attached to a respective opposite side of said bulldozer body; a blade pivotally attached to the distal ends of said frame members, said blade having opposite transverse ends and a traditional range of blade edge angles; first and second hydraulic cylinders, each of said first and second hydraulic cylinders pivotally coupling between a respective transverse end of said blade and an intermediate portion of a respective one of said first and second frame members; and a hydraulic drive system for said first and second hydraulic cylinders, said hydraulic drive system comprising at least one hydraulic pump for supplying a hydraulic fluid to said first and second hydraulic cylinders, directional control valves for controlling the supplying of the hydraulic fluid from said at least one hydraulic pump to said first and second hydraulic cylinders, whereby said first and second hydraulic cylinders can be extended or contracted by said hydraulic drive system so that said blade can be inclined forwardly or rearwardly, whereby in said traditional range of blade edge angles earth-moving work is performed under a condition wherein an operator controls said blade by applying a force to said blade so that said blade is pressed downwardly against a ground surface such that a front portion of the bulldozer body is apt to lift upwardly, thereby reducing a traction force of said apparatus with respect to a ground surface, the improvement comprising each of said first and second hydraulic cylinders having a length such that said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade with respect to the posture of said blade in said traditional range of blade edge angles, such that at said rearwardly inclined angle of said blade earth-moving work can be performed under a condition wherein a weight of earth loaded on said blade is sufficiently greater, than an amount of earth loaded on said blade when positioned in said traditional range, so that the greater weight of the thus loaded earth acts on said blade in such a manner as to cause said blade to bite into the ground surface so that an operator controls said blade by applying a lifting force to said blade, thereby causing said front end of said bulldozer body to be pressed downwardly against the ground surface so as provide a substantially uniform ground contact pressure.

Claim 56

An apparatus in accordance with claim 44, wherein said blade has a concave front panel and a blade edge member attached to a lower end of said concave front panel such that at said rearwardly inclined angle of said blade, an angle between a horizontal line and a line tangential to said lower end of said concave front panel is about 35°.

Claim 57

Apparatus in accordance with claim 44, wherein each of said first and second hydraulic cylinders has a length such that said first and second hydraulic cylinders are able to control said blade at a rearwardly inclined angle of said blade in the range of about 5° to about 20° with respect to said traditional range in order to provide an earth-moving posture of said blade for performing earth-moving which is inclined more rearwardly than said traditional range.

Claim 58

Apparatus in accordance with claim 44, wherein said traditional range of blade edge angles is 55°± about 5°.

Claim 59

An apparatus in accordance with claim 44, wherein each of said first and second hydraulic cylinders has a length such that said first and second hydraulic cylinders are able to control said blade at a blade edge angle which is equal to or less than about 45°.

Claim 60

An apparatus in accordance with claim 44, wherein said blade has a blade edge member extending along a lower end of said blade, said blade edge member having a front face to form a blade edge angle between said front face of said blade edge member and a horizontal line when said blade is placed on the ground, wherein said digging posture includes a blade edge angle of 55°± about 5°, and wherein each of said first and second hydraulic cylinders has a length such that said first and second hydraulic cylinders are able to control said blade at a blade edge angle equal to or less than about 45°.

Claim 61

An apparatus in accordance with claim 44, wherein said blade has a concave front panel, and a blade edge member is attached to said blade at a lower end of said concave front panel such that a line tangential to said lower end of said concave front panel is inclined rearwardly with respect to a front surface of said blade edge member.

Claim 62

An apparatus in accordance with claim 50, wherein said line tangential to said lower end of said concave front panel is inclined rearwardly with respect to said front surface of said blade edge member at an angle which is greater than zero and less than or equal to about 15°.

Claim 63

An apparatus in accordance with claim 50, wherein said line tangential to said lower end of said concave front panel is inclined rearwardly with respect to said front surface of said blade edge member at an angle which is in the range of about 10° to about 15°.

Claim 64

An apparatus in accordance with claim 44, wherein said first and second hydraulic cylinders are also able to control said blade at a forwardly inclined angle of said blade in the range of about 5° to about 45° with respect to said digging posture of said blade.

Claim 65

An apparatus in accordance with claim 53, wherein said hydraulic drive system further comprises a changeover control circuit for changing between a tilt mode and a pitch mode, wherein said at least one hydraulic pump comprises at least one main hydraulic pump for supplying said hydraulic fluid to said first and second hydraulic cylinders and at least one assistant hydraulic pump for assisting said at least one main hydraulic pump in supplying said hydraulic fluid to said first and second hydraulic cylinders, wherein said changeover control circuit includes at least one assistant solenoid selector valve and a speed changeover device, wherein each said at least one assistant hydraulic pump is selectively connectable through a respective one of said at least one assistant solenoid selector valve to a delivery line of a respective one of said at least one main hydraulic pump to thereby assist the respective main hydraulic pump in supplying hydraulic fluid to at least one of said first and second hydraulic cylinders at a delivery rate, which is greater than a delivery rate which would be provided by only the respective main hydraulic pump, to thereby operate at least one of said first and second hydraulic cylinders at a speed which is higher than a speed which would be provided by only the respective main hydraulic pump, and wherein said speed changeover device provides a signal to at least one assistant solenoid selector valve to connect the respective assistant hydraulic pump to the respective delivery line when the respective assistant hydraulic pump is to assist the respective main hydraulic pump.

Claim 66

An apparatus in accordance with claim 53, wherein said at least one hydraulic pump comprises at least one variable displacement hydraulic pump which is controlled by an external signal.

Claim 67

An apparatus in accordance with claim 53, wherein said hydraulic drive system further comprises a changeover control circuit for changing between a tilt mode and a pitch mode, wherein said at least one hydraulic pump comprises at least one fixed displacement hydraulic pump, wherein said changeover control circuit includes a plurality of solenoid selector valves, and wherein a delivery line of at least one of said at least one fixed displacement hydraulic pump is connectable through one of said directional control valves to a bottom-side line of said first hydraulic cylinder, a head-side line of said first hydraulic cylinder is connectable to a bottom-side line of said second hydraulic cylinder through one of said plurality of solenoid selector valves, and a head-side line of said second hydraulic cylinder is connectable to a drain line through another one of said plurality of solenoid selector valves and one of said directional control valves, thereby making up a series circuit.

Claim 72

An apparatus in accordance with claim 58, wherein said pitch range is at least about 40°.

Claim 73

An apparatus in accordance with claim 58, wherein a line tangential to said lower edge of said concave front panel is inclined rearwardly with respect to a front surface of said blade edge member at an angle which is in the range of greater than zero to about 15°.

Claim 74

An apparatus in accordance with claim 58, wherein said second value is at least about 10° from said first value, and said third value is at least about 30° from said first value.

Claim 77

A method in accordance with claim 62, wherein the thus formed predetermined rearwardly inclined angle is in the range of about 5° to about 20°.

Claim 78

A method in accordance with claim 62, wherein the thus formed predetermined rearwardly inclined angle is in the range of about 10° to about 20°.

Claim 79

A method in accordance with claim 62, further comprising: performing earth-dumping work by inclining said blade forwardly by a predetermined angle with respect to said digging posture of said blade in order to provide an earth-dumping posture of said blade for performing earth-dumping which is inclined more forwardly than said digging posture of said blade, thereby enabling the earth to be easily dumped from said blade.

Claim 80

A method in accordance with claim 65, wherein the thus formed predetermined forwardly inclined angle is in the range of about 5° to about 45°.

Claim 81

A method in accordance with claim 65, wherein the thus formed predetermined forwardly inclined angle is in the range of about 10° to about 45°.

Claim 82

A method in accordance with claim 65, wherein the thus formed predetermined rearwardly inclined angle is in the range of about 10° to about 20°, and wherein the thus formed predetermined forwardly inclined angle is in the range of about 10° to about 45°.

Claim 83

A method in accordance with claim 62, wherein said bulldozer body is provided with a tilt/pitch changeover means for controlling said blade to incline said blade forwardly or rearwardly, a pitch speed changeover means, and a control means for raising and lowering said blade, said method further comprising: selecting a desired one of a posture for digging work, a posture for earth-moving work, and a posture for earth-dumping work by operating said tilt/pitch changeover means, said pitch speed changeover means, and said control means.

Claim 84

A method in accordance with claim 62, wherein said bulldozer body is provided with a pitch-dump selector means for controlling said blade to incline said blade forwardly or rearwardly, a pitch-back selector means, and a control means for raising and lowering said blade, said method further comprising: selecting a desired one of a posture for digging work, a posture for earth-moving work, and a posture for earth-dumping work by operating said pitch-dump selector means, said pitch-back selector means, and said control means.

Claim 87

A method in accordance with claim 71, wherein said pitch range is at least about 40°.

Claim 88

A method in accordance with claim 71, wherein a line tangential to said lower edge of said concave front panel is inclined rearwardly with respect to a front surface of said blade edge member at an angle which is in the range of greater than zero to about 15°.

Claim 89

A method in accordance with claim 71, wherein said second value is at least about 10° from said first value, and said third value is at least about 30° from said first value.