Road levelling machine

Claim 2

A road levelling machine comprising: a chassis mounted on road wheels adapted to travel along a road to be levelled; power driving means connected to said road wheels for propelling the chassis along the road; power driven hammer means, mounted on the chassis and having cutting heads adapted to engage the road surface, for imparting through the cutting heads a succession of impact blows to the road so as to cut away the top surface thereof below the cutting heads; sensing means mounted on the chassis for detecting height irregularities in the road surface along tthe path of travel of the machine; and speed control means for regulating the speed of travel of the chassis in response to detection by said sensing means of height irregularities in the road surface.

Claim 3

A road levelling machine as claimed in claim 1, wherein said speed control means are operable to regulate said driving means to decrease the speed of travel of the machine in response to operation of said hammer means.

Claim 4

A road levelling machine as claimed in claim 1 further including hammer control means for operating said hammer means in response to detection by said sensing means of height irregularities in the road surface.

Claim 5

A road levelling machine comprising: a chassis mounted on roAd wheels adapted to travel along a road to be levelled; power driving means connected to said road wheels for propelling the chassis along the road; power driven hammer means, mounted on the chassis and having cutting heads adapted to engage the road surface, for imparting through the cutting heads a succession of impact blows to the road so as to cut away the top surface thereof below the cutting heads, the road wheels mounted on the chassis to the rear of said hammer means being arranged to run on the part of the road surface cut away by said hammer means; sensing means mounted on the chassis for detecting any difference in height between the chassis and the road surface immediately to the rear of said hammer means during travel along the road; and speed control means for regulating said driving means to increase or decrease the speed of travel of the machine in response to detection by said sensing means of an increase or decrease respectively in said height difference.

Claim 6

A road levelling machine comprising: a chassis mounted on roAd wheels adapted to travel along a road to be levelled; power driving means connected to said road wheels for propelling the chassis along the road; power driven hammer means, mounted on the chassis and having cutting heads adapted to engage the road surface, for imparting through the cutting heads a succession of impact blows to the road so as to cut away the top surface thereof below the cutting heads, the road wheels mounted on the chassis to the rear of said hammer means being arranged to run on the part of the road surface cut away by said hammer means; sensing means mounted on the chassis for detecting any difference in height between the chassis and the road surface immediately to the rear of said hammer means during travel along the road; and speed control means for regulating said driving means to increase or decrease the speed of travel of the machine in response to detection by said sensing means of an increase or decrease respectively in said height difference.

Claim 7

A road levelling machine as claimed in claim 4, wherein the cutting heads are spaced across the chassis, and further including reciprocating means for reciprocating the hammer means in directions transverse to the direction of travel of the chassis and through distances such that the paths of travel of each cutting head overlaps the paths of travel of the adjacent cutting heads.

Claim 8

A road levelling machine as claimed in claim 4, further including: additional sensing means mounted on the chassis for detecting the difference in height between the chassis and the part of the road surface below or immediately ahead of the hammer means in the direction of travel; and additional speed control means for regulating said driving means to decrease the speed of travel of the machine in response to detection by said additional sensing means of a height difference below a predetermined value.

Claim 9

A road levelling machine as claimed in claim 6 further including hammer control means for operating said hammer means in response to detection by said additional sensing means of height irregularities in the road surface.

Claim 10

A road levelling machine as claimed in claim 4 wherein said hammer means comprises: a cylinder member; a piston member mounted in said cylinder member and having a piston rod projecting out through a bore in one end of said cylinder member, the piston and cylinder members cooperating to form first and second chambers, the volume of said first chamber increasing upon relative movement of the two members towards a fully extended position and the volume of said second chamber increasing upon relative movement of the two members towards a fully retracted position; and valve means for feeding fluid under pressure to said chambers and for exhausting fluid from at least one of said chambers so as to cause reciprocating movement between the piston and cylinder members, one of said members being mounted on the chassis and a cutting head being fitted on the lower end of the other member, wherein said valve means includes inlet and exhaust ports controlled by relative movements of the piston and cylinder members, and said ports are arranged so that, upon relative movement of the piston and cylinder members into their fully extended position said first chamber is connected to the inlet port and disconnected from the exhaust port, whereby the pressure of fluid in said first chamber tends to hold the piston and cylinder members in their fully extended position.

Claim 11

A road levelling machine as claimed in claim 8, wherein said cylinder is mounted in a substantially upright position on the chassis, said piston road extending downwardly as a close sliding fit through a bore in the lower end of said cylinder, and said cutting head is mounted on the lower end of said piston rod, said first chamber being formed between said piston and the upper end of said cylinder and said second chamber being formed between said piston, said piston rod, and the lower end of said cylinder, and said valve means comprises an inlet port opening into the lower end portion of said cylinder, an exhaust port opening into the bore through which said piston rod extends, a transfer duct in said piston and piston rod opening through the top of said piston into the upper end portion of said cylinder, a transverse inlet duct in said piston rod effecting communication between the lower end portion of said cylinder and said transfer duct when said piston is in the upper end portion of said cylinder, said transverse inlet duct being closed by the wall of said piston rod bore when the piston is in the lower end portion of said cylinder, and a transverse exhaust duct in said piston rod effecting communication between said exhaust port and said transfer duct when said piston is in the lower end portion of said cylinder, said transverse exhaust duct being closed by the wall of said piston rod bore when said piston is in the upper end portion of said cylinder and also when said piston is abutting the bottom end wall of said cylinder by a distance slightly greater than the depth of said piston whereby fluid from said inlet port flows into the upper end portion of said cylinder whenever said piston drops below a level at which the top of said piston uncovers said inlet port and thereby holds said piston against the bottom end wall of said cylinder.