There is disclosed a set of golf irons which have progressively decreasing displacements between the axis of the shaft and the center of mass projected to the horizontal plane beginning with the long irons and progressing to the short irons.

Each iron in the set also has a support column behind the striking face, parabolic shaped horizontal grooves in the striking face with a top junction between the striking face and each groove, the top junction and groove sides defined by a segment of a parabola, the longest groove length in the striking face of each club proportional to the club displacement, and a flat segment on the sole.

This invention relates generally to golf irons and more particularly concerns a set of golf irons including long distance irons and short distance irons which set, beginning with the long irons, has progressively descreasing displacement betweenthe center line of the hosel and the center of mass of the head. In addition each iron within the set has a support column in a cavity behind the center of mass of the head, a pattern of horizontal face grooves with parabolic sides which pattern ofgrooves is configured to disguise the progressive displacement, and a planar segment on the sole to cause the head to sit squarely at address.

Golf irons typically include a set of eleven irons, numbered one (long) through nine (short), a pitching wedge, and a sand wedge. Each iron comprises a head including a hosel and a shaft which is attached to the head by fitting the shaft intothe bore of the hosel. The hosel is attached to and is integral with the head. The head includes a heel, a bottom sole, a toe, a planar striking face, and a backside.

The eleven irons of a set conventionally have varying degrees of loft angle and lie angle. The loft angle of an iron is the angle between a vertical plane, which includes the shaft, and the plane of the striking face of the iron. The lie angleof an iron is the angle between the shaft and the ground (horizontal plane) when the tangent to the sole directly under the center of mass is in the horizontal plane and when the shaft lies in a vertical plane.

The loft angle, as the name suggests, determines how much loft is imparted to the ball when it is stuck by the tilted striking face. The lie angle of the iron assures that, when swung properly, the sole of the iron will contact the ground evenlyso that the striking face will not tend to twist inwardly or outwardly.

For any set of golf irons, it is important that for a consistent swing, the iron impart consistent loft and distance to the ball. It is also important that when properly swung, the iron produces a consistent shot without tendency to hook orslice.

Even when conventional irons are swung consistently, such irons vary in their loft change at impact due to centrifugal forces. The prior art teaches that that tendency to change loft can be compensated for by providing a set of golf irons whichhave progressively decreasing offsets, beginning with the long iron (#1) and progressively decreasing toward the short irons (sand wedge). The offset is the distance between the leading edge of the face of the iron and the axis of the shaft in thehorizontal direction into the striking face of the iron (Y-direction). For long irons, the leading edge of the face actually trails the axis of the shaft. For short irons, the leading edge of the face actually proceeds the axis of the shaft. Theoffset is related to the distance by which the center of mass of the head trails the axis of the shaft. The center of mass for short irons trails the axis of the shaft by more than the center of mass for long irons trails the axis of the shaft.

Because of the offset and the related position of the center of mass, the centrifugal forces that result about the center of mass of the head when the iron is swung tend to cause the iron to increase its loft angle as the shaft bends and to causethe head to twist about the shaft axis toward a more closed face position as the face of the iron comes into contact with the ball. By progressively varying the offset from the long irons to the short irons, an appropriate degree of consistent loftchange can be achieved from iron to iron.

Offset in a conventional set of irons also tends to induce a twisting action at the head which closes the face and produces a hook. That twisting action is greater for the short irons with their larger head mass than for the long irons withtheir smaller head mass.

It is also well known in the art to design golf irons with the majority of the weight concentrated at the heel and toe of the iron in order to increase the moment of inertial about the center of mass of the irons so that the head will not tend totwist if the ball is struck slightly off center. Such weight distribution is generally accomplished by providing a cavity in the backside of the iron centered about the center of mass so that the remaining mass of the head of the iron is concentrated atthe heel and toe. Because of the cavity in the backside of the iron, the iron has a very thin blade at the center of mass directly behind the striking face. Consequently, when a ball is struck with such a thin bladed iron, the iron produces a hollowsound which is considered objectionable by many golfers.

It is therefore an object of the present invention to provide a set of golf irons including long irons and short irons which have a progressively decreasing offset, beginning with the long irons, and a progressively decreasing displacement,beginning with the long irons, where the displacement is measured along the ground (horizontal plane) between the intersection of the ground and a line through the center of mass projected perpendicularly toward the leading edge of the face and theintersection of the ground and the axis of the shaft projected toward the ground.