Belt grinding machine

Claim 2

A grinding machine for grinding the surfaces of workpieces comprising a. an endless grinding belt, b. means for conveying workpieces along a path towards and adjacent to the operative length of said belt, said path being transverse to the direction of movement of said grinding belt, c. means for releasably applying grinding pressure to the operative length of said belt, d. workpiece sensing means for detecting the leading and trailing edges of workpieces on said conveying means at a point along said path upstream of said grinding belt and for activating said pressure applying means when a leading edge is detected and deactivating said pressure applying means when a trailing edge is detected, and e. delay means for delaying the application and release of pressure by said pressure applying means following activation and deactivation respectively of said pressure applying means, said delay means providing a first delay period from the time said sensing means detects the leading edge of said workpiece to the time said leading edge has advanced to a position adjacent said belt before pressure is applied to said belt and providing a second delay period from the time said sensing means detects the trailing edge of said workpieces to the time said trailing edge has advanced to a position adjacent said belt before pressure is released from said belt, said first delay period being longer than said second delay period, f. whereby the surfaces of the workpieces may be ground without grinding down or damaging the edges of the workpieces.

Claim 3

A grinding machine as claimed in claim 1 wherein a. said pressure applying means comprises an elongated elastic plate arranged adjacent to the operative length of the belt, means biasing said plate towards said belt to apply pressure to said plate, and a plurality of retraction means, each for withdrawing pressure applied by a different portion of the length of said elastic plate, b. said sensing means comprises a plurality of individual sensing elements arranged across said path upstream from said grinding belt, each for Releasing one of said retraction means when detecting a workpiece and for actuating said retraction means when not detecting a workpiece, and c. said delay means comprises a first and a second delay device operatively associated with each of said retraction means and the sensing element for controlling it, said first delay device being adapted to retard release of said retraction means and the application of pressure to said belt and said second delay device being adapted to retard actuation of said retraction means to withdraw application of pressure to said belt, d. whereby full pressure will be applied to only substantially that portion of the operative length of the grinding belt corresponding to the width of the workpiece and to the number and location of the sensing devices operated by the workpiece.

Claim 4

A grinding machine as claimed in claim 2 wherein each retraction means comprises a piston-cylinder arrangement operable by a pressure medium.

Claim 5

A grinding machine as claimed in claim 3 further comprising valve means operatively connected to each sensing element for controlling the application and release of said pressure medium to each piston-cylinder arrangement.

Claim 6

A grinding machine as claimed in claim 2 wherein said sensing elements comprise pivotally mounted sensing levers and entraining means for coupling neighboring sensing levers such that sensing levers directly deflected by contact with the workpiece operate to deflect adjacent sensing levers to a lesser extent whereby portions of said elastic plate beyond the sides of the workpiece apply a lesser pressure to the operative length of said belt.

Claim 7

A grinding machine as claimed in claim 5 wherein said entraining means comprises a plurality of entraining arms, one arm being attached to each of said sensing levers and extending transversely therefrom a sufficient distance to engage and deflect adjacent entraining arms.

Claim 8

A grinding machine as claimed in claim 3 wherein said piston-cylinder arrangement further comprises a push rod connected to said piston and mechanical means releasably connecting said push rod with a portion of said elastic plate and said first delay device comprises means to retard movement of said mechanical means in the direction to cause said portion of said elastic plate to apply pressure to said belt for a predetermined time after said push rod is moved in said direction.

Claim 9

A grinding machine as claimed in claim 7 wherein said means to retard movement of said mechanical means comprises a pawl and cam means on said push rod for acting on said pawl as said push rod moves in the direction to cause pressure to be applied to said belt.

Claim 10

A grinding machine as claimed in claim 8 further comprising spring means biasing said pawl towards said cam means.

Claim 11

A grinding machine as claimed in claim 3 further comprising valve means operatively connected to said sensing means for controlling said pressure medium flowing to and from said piston-cylinder arrangement and wherein said second delay device comprises throttle valve means for controlling the rate of flow of said pressure medium to the piston in said piston-cylinder arrangement to withdraw a portion of said elastic plate whereby said elastic plate may be retained in a position applying pressure to said belt for a predetermined time after the trailing edge of said workpiece has passed said sensing device.

Claim 12

A grinding machine as claimed in claim 10 wherein said throttle valve means comprises means for adjusting the cross-section of flow through said throttle valve means whereby the period of delay after the trailing edge of the workpiece passes said sensing means and before the elastic plate is moved away from said belt may be controlled.

Claim 13

In a grinding machine for grinding the surfaces of workpieces and including means for conveying workpieces along a path past and in contact with the operative length of an endless grinding belt, the improvement comprising a. a plurality of sensing meanS extending transversely across said path upstream from said grinding belt to detect the presence of each workpiece on said conveyor means as it approaches said grinding belt, b. a plurality of pressure applying means arranged to press said grinding belt against workpieces while being conveyed past said belt, c. a plurality of means for moving said pressure applying means towards and away from said belt, said moving means being responsive to said sensing means such that detection of the presence of a workpiece by said sensing means causes said pressure applying means to press said belt against said workpiece and detection of no workpiece causes said pressure applying means to be withdrawn, and d. delay means to delay movement of said pressure applying means towards and away from said belt such that said belt is not pressed by said pressure applying means until grinding action begins on a workpiece, the leading edge of which was previously detected upstream by said sensing means, and pressure on said belt by said pressure applying means is not released until grinding action terminates on said workpiece, the trailing edge of which was previously detected upstream by said sensing means, said delay means comprising pawl means to retain said pressure applying means in withdrawn position and cam means on said moving means to release said pawl means after movement of said moving means a predetermined distance following detection of the leading edge of a workpiece by said sensing means e. whereby the surface of the workpiece may be ground without grinding down or damaging the edges of the workpieces.

Claim 14

In a grinding machine for grinding the surfaces of workpieces and including means for conveying workpieces along a path past and in contact with the operative length of an endless grinding belt, the improvement comprising a. a plurality of sensing meanS extending transversely across said path upstream from said grinding belt to detect the presence of each workpiece on said conveyor means as it approaches said grinding belt, b. a plurality of pressure applying means arranged to press said grinding belt against workpieces while being conveyed past said belt, c. a plurality of means for moving said pressure applying means towards and away from said belt, said moving means being responsive to said sensing means such that detection of the presence of a workpiece by said sensing means causes said pressure applying means to press said belt against said workpiece and detection of no workpiece causes said pressure applying means to be withdrawn, and d. delay means to delay movement of said pressure applying means towards and away from said belt such that said belt is not pressed by said pressure applying means until grinding action begins on a workpiece, the leading edge of which was previously detected upstream by said sensing means, and pressure on said belt by said pressure applying means is not released until grinding action terminates on said workpiece, the trailing edge of which was previously detected upstream by said sensing means, said delay means comprising pawl means to retain said pressure applying means in withdrawn position and cam means on said moving means to release said pawl means after movement of said moving means a predetermined distance following detection of the leading edge of a workpiece by said sensing means e. whereby the surface of the workpiece may be ground without grinding down or damaging the edges of the workpieces.

Claim 15

In a grinding machine for grinding the surfaces of workpieces and including means for conveying workpieces along a path past and in contact with the operative length of an endless grinding belt, the improvement comprising a. a plurality of sensing means extending transversely across said path upstream from said grinding belt to detect the presence of each workpiece on said conveyor means as it approaches said grinding belt, b. a plurality of pressure applying means arranged to press said grinding belt against workpieces while being conveyed past said belt, c. a plurality of means for moving said pressure applying means towards and away from said belt, said moving means being responsive to said sensing means such that detection of the presence of a workpiece by said sensing means causes said pressure applying means to press said belt against said workpiece and detection of no workpiece causes said pressure applying means to be withdrawn, and d. delay means to delay movement of said pressure applying means towards and away from said belt such that said belt is not pressed by said pressure applying means until grinding action begins on a workpiece, the leading edge of which was previously detected upstream by said sensing means, and pressure on said belt by said pressure applying means is not released until grinding action terminates on said workpiece, the trailing edge of which was previously detected upstream by said sensing means, e. said moving means comprising fluid pressure operated means and said delay means comprising throttle valve means responsive to said sensing means for controlling the flow of pressure fluid to and from said fluid pressure operated means such that said fluid pressure means is not moved and said pressure applying means is retained against said belt until predetermined volumes of fluid to and from said fluid pressure operated means have passed through said throttle valve means following detection of the trailing edge of a workpiece by said sensing means f. whereby the surface of the workpiece may be ground without grinding down or damaging the edges of the workpieces.

Claim 16

In a grinding machine for grinding the surfaces of workpieces and including means for conveying workpieces along a path past and in contact with the operative length of an endless grinding belt, the improvement comprising a. a plurality of sensing means extending transversely across said path upstream from said grinding belt to detect the presence of each workpiece on said conveyor means as it approaches said grinding belt, b. a plurality of pressure applying means arranged to press said grinding belt against workpieces while being conveyed past said belt, c. a plurality of means for moving said pressure applying means towards and away from said belt, said moving means being responsive to said sensing means such that detection of the presence of a workpiece by said sensing means causes said pressure applying means to press said belt against said workpiece and detection of no workpiece causes said pressure applying means to be withdrawn, and d. delay means to delay movement of said pressure applying means towards and away from said belt such that said belt is not pressed by said pressure applying means until grinding action begins on a workpiece, the leading edge of which was previously detected upstream by said sensing means, and pressure on said belt by said pressure applying means is not released until grinding action terminates on said workpiece, the trailing edge of which was previously detected upstream by said sensing means, e. said moving means comprising fluid pressure operated means and said delay means comprising throttle valve means responsive to said sensing means for controlling the flow of pressure fluid to and from said fluid pressure operated means such that said fluid pressure means is not moved and said pressure applying means is retained against said belt until predetermined volumes of fluid to and from said fluid pressure operated means have passed through said throttle valve means following detection of the trailing edge of a workpiece by said sensing means f. whereby the surface of the workpiece may be ground without grinding down or damaging the edges of the workpieces.