Apparatus and method for converting sheet folder to booklet maker

Claim 2

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means located above and on said one side of said pair of rollers and inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets in a straight-line path from said stapling mechanism down to said pair of rollers; stop means in said guide means spaced from said stapling mechanism by substantially half the length of each sheet and normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers and to position the longitudinal midpoint of each sheet beneath said stapling mechanism; and means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers.

Claim 3

The combination of claim 1 wherein said guide means comprises: lower guide plate means inclining down toward said pair of rollers, said lower guide plate means extending forward from said stapling station toward said pair of rollers and extending behind said stapling station; and laterally spaced holders extending up from said lower guide plate means behind and in front of said stapling station for slidably receiving between them, and for engaging the opposite side edges of, a stack of sheets to be stapled and folded into a booklet.

Claim 4

The combination of claim 2 and further comprising: vibratory jogging members on one of said holders for pushing the stack of sheets against the other of said holders.

Claim 5

The combination of claim 3 and further comprising: means for selectively adjusting said holders toward and away from each other.

Claim 6

The combination of claim 2 and further comprising: means for selectively adjusting said holders toward and away from each other.

Claim 7

The combination of claim 4 wherein: said lower guide plate means is apertured to pass said stop means; and further comprising: means normally positioning said stop means to extend up through said apertured lower guide plate means in front of said stapling station for engagement by the leading edge of a stack of sheets in said stapling station; and means for lowering said stop means below said lower guide plate means to permit a stapled set of sheets to slide down said lower guide plate means to said pair of rollers.

Claim 8

The combination of claim 1 and further comprising: means for jogging the stack of sheets in said stapling station to align their edges.

Claim 9

The combination of claim 1 wherein: said guide means comprises an apertured lower guide plate inclining down from said stapling station to said pair of rollers; and further comprising: means for normally positioning said stop means to extend up through said apertured lower guide plate for engagement with the leading edge of each of a stack of sheets in said stapling station; and means for lowering said stop means below said lower guide plate to permit a stapled set of said sheets to slide down said lower guide plate to said pair of rollers.

Claim 10

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers, said guide means comprising: lower guide means inclining down toward said pair of rollers, said lower guide plate means extending forward from said stapling station toward said pair of rollers and extending behind said stapling station, laterally spaced holders extending up from said lower guide plate means behind and in front of said stapling station for slidably receiving between them a stack of sheets to be stapled and folded into a booklet, and means for selectively adjusting said holders toward and away from each other; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; said lower guide plate means being apertured to pass said stop means; means normally positioning said stop means to extend up through said apertured lower guide plate means in front of said stapling station for engagement by the leading edge of a stack of sheets in said stapling station; means for lowering said stop means below said lower guide plate means to permit a stapled set of sheets to slide down said lower guide plate means to said pair of rollers; and means for selectively adjusting said stop means along said lower guide plate means toward and away from said stapling station.

Claim 11

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers, said guide means comprising: lower guide means inclining down toward said pair of rollers, said lower guide plate means extending forward from said stapling station toward said pair of rollers and extending behind said stapling station, laterally spaced holders extending up from said lower guide plate means behind and in front of said stapling station for slidably receiving between them a stack of sheets to be stapled and folded into a booklet, and means for selectively adjusting said holders toward and away from each other; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; said lower guide plate means being apertured to pass said stop means; means normally positioning said stop means to extend up through said apertured lower guide plate means in front of said stapling station for engagement by the leading edge of a stack of sheets in said stapling station; means for lowering said stop means below said lower guide plate means to permit a stapled set of sheets to slide down said lower guide plate means to said pair of rollers; and means for selectively adjusting said stop means along said lower guide plate means toward and away from said stapling station.

Claim 12

The combination of claim 9 and further comprising: a kicker plate below said lower guide plate means near said stapling station; means normally positioning said kicker plate below said guide plate means; said lower guide plate means having an opening therein for passing said kicker plate; and means for moving said kicker plate up through said opening in said lower guide plate means to strike the stapled set of sheets from below in timed relation with the lowering of said stop means.

Claim 13

The combination of claim 10 and further comprising: means for selectively adjusting said third roller vertically to provide a corresponding gap between said third roller and said one roller of said pair of rollers.

Claim 14

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; said guide means comprising an apertured lower guide plate inclining down from said stapling station to said pair of rollers; means for normally positioning said stop means to extend up through said apertured lower guide plate for engagement with the leading edge of each of a stack of sheets in said stapling station; means for lowering said stop means below said lower guide plate to permit a stapled set of said sheets to slide down said lower guide plate to said pair of rollers; and means for selectively adjusting said stop means along said apertured lower guide plate toward and away from said stapling station.

Claim 15

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; said guide means comprising an apertured lower guide plate inclining down from said stapling station to said pair of rollers; means for normally positioning said stop means to extend up through said apertured lower guide plate for engagement with the leading edge of each of a stack of sheets in said stapling station; means for lowering said stop means below said lower guide plate to permit a stapled set of said sheets to slide down said lower guide plate to said pair of rollers; and means for selectively adjusting said stop means along said apertured lower guide plate toward and away from said stapling station.

Claim 16

The combination of claim 12 and further comprising: a kicker plate below said lower guide plate near said stapling station; means normally positioning said kicker plate below said lower guide plate; said lower guide plate having an opening therein for passing said kicker plate; and means for moving said kicker plate up through said opening in said lower guide plate to strike the stapled set of sheets from below in timed relation with the lowering of said stop means.

Claim 17

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; and means for selectively adjusting said stop means along said guide means toward and away from said stapling station.

Claim 18

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; and means for selectively adjusting said stop means along said guide means toward and away from said stapling station.

Claim 19

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; and a kicker plate at said stapling station operable to strike the stapled set of sheets from below in timed relation with the retraction of said stop means from engagement by the leading edge of said stapled set of sheets.

Claim 20

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; and a kicker plate at said stapling station operable to strike the stapled set of sheets from below in timed relation with the retraction of said stop means from engagement by the leading edge of said stapled set of sheets.

Claim 21

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; and means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism stapled said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; and means for selectively adjusting said third roller vertically to provide a corresponding gap between said third roller and said one roller of said pair of rollers.

Claim 22

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; and means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism stapled said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; and means for selectively adjusting said third roller vertically to provide a corresponding gap between said third roller and said one roller of said pair of rollers.

Claim 23

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; means on said guide means providing a calibrated scale displaying the distance forward from said stapling station; and means for adjusting said stop means along said scale toward and away from said stapling station.

Claim 24

In combination with a folder having: a pair of power-driven rollers operatively arranged to pull down between them a stapled set of sheets of paper; guide members extending down from said pair of rollers on one side thereof, said guide members defining a downwardly inclined guide recess located on said one side of said pair of rollers, said guide recess having an open upper end positioned to receive the stapled set of sheets pulled down by said pair of rollers; a stop member positioned in said guide recess in the path of said stapled set of sheets for engagement by the leading edge of said stapled set of sheets to prevent the continued advance of said set of sheets down into said guide recess; and a third roller positioned below one of said pair of rollers and cooperable therewith to define a fold gap through which said stapled set of sheets is pulled after said leading edge of said stapled set of sheets engages said stop member and the trailing part of the stapled set of sheets continues to be pulled down between said pair of rollers; the improvement which comprises a stapling and guide unit attached to said folder above said pair of rollers, said stapling and guide means having: a stapling station including a power-operated stapling mechanism located above and on said one side of said pair of rollers; guide means inclined downward and forward from said stapling station toward said pair of rollers for passing a stapled set of sheets from said stapling mechanism down to said pair of rollers; stop means in said guide means normally positioned for engagement by the leading edge of a stack of sheets in said stapling station to hold said stack against movement down said guide means to said pair of rollers; means for retracting said stop means from engagement by the leading edge of said stack of sheets when said stapling mechanism staples said stack into a stapled set of said sheets, thereby permitting said stapled set of sheets to pass down said guide means to said pair of rollers; means on said guide means providing a calibrated scale displaying the distance forward from said stapling station; and means for adjusting said stop means along said scale toward and away from said stapling station.

Claim 25

The combination of claim 17 wherein: said means for adjusting said stop means comprises a positioning rod extending below said guide means and elongated lengthwise of said scale, said rod having a plurality of recesses therein spaced apart along its length; and further comprising: a cross wall having an opening therein which passes said positioning rod; and spring means biasing said positioning rod against an edge of said opening to releasable hold said rod in said cross wall at a selected one of recesses in the rod.