Stapling machine

Claim 2

A stapling machine comprising support means; combined bending and cutting means comprising a stationary die having a cutting edge and being mounted on said support means, a retractable anvil mounted on said support means spaced from said die and being movable between an active and a withdrawn position, a pair of spaced punches reciprocable in a predetermined direction, one of said punches having a cutting edge cooperating with the cutting edge of said die and being located between said die and one side of said anvil, and the other being located on the other side of said anvil, said punches cooperating with said die and said anvil for cutting off a portion of a wire fed between said die and said punches, for then bending the cut-off wire portion into a Ushaped staple and for subsequently moving the U-shaped staple downwardly, means biasing said retractable anvil to said active position, and means for moving said anvil to said retracted position after the wire portion has been bent into a U-shaped staple; clinching means comprising a clinching anviL mounted on said support means downwardly spaced from said retractable anvil and a clincher located between and reciprocable in the same direction as said punches and cooperating with said clinching anvil for clinching the U-shaped staple; a carrier member carrying said two punches spaced from each other; a driver member mounted on said support means reciprocable in said predetermined direction and carrying said clincher for movement therewith; moving means connected to said driver member for moving the same along an active stroke from an upper rest position to a lower end position in which said clincher clinches said U-shaped staple and along a return stroke back to said rest position; coupling means movable between a coupling position and an uncoupling position for connecting, when in said coupling position, said carrier member to said driver member for movement along said active stroke; cooperating stop means on said support means and said carrier member for stopping the movement of the latter after said punches mounted thereon have bent said cut-off wire portion into a U-shaped staple and moved the latter towards said clinching anvil; means cooperating with said coupling means after stopping of said carrier member and further movement of said driver member along its active stroke for moving said coupling means to said uncoupling position so as to permit said clincher carried by said driver member to move downwardly relative to said punches to clinch the staple; means to return said coupling means to said coupling position during movement of said driver member along its return stroke; and additional means between said carrier member and said driver member for moving said carrier member with said driver member during the return stroke of the latter while positioning said carrier member relative to said driver member for permitting movement of said coupling means to said coupling position, said additional means comprising an elongated slot formed in one of said members, a pin fixed to the other of said members and additional biasing means for yieldably maintaining said pin in engagement with one end of said slot.

Claim 3

A stapling machine as defined in claim 1, wherein said coupling means comprises a roller, a pair of abutment means respectively provided on said driver member and said carrier member to respectively engage said roller on opposite portions of its peripheral surface, and guide face means on said support means for maintaining said roller between said pair of abutment means, and wherein said means for moving said coupling means to said uncoupling position comprise a cam face on one of said abutment means inclined to said predetermined direction in such a manner to push said roller toward said guide face means, and a pocket in said guide face means laterally aligned with said roller in the position the latter reaches when said carrier member is stopped by said stop means so that said roller will move by the action of said cam face into said pocket and out of engagement with said abutment means on said carrier member permitting thereby said driver member to continue its movement while said carrier member is stopped.

Claim 4

A stapling machine as defined in claim 2, wherein said cam face is provided on said abutment means of said driver member and wherein said abutment means on said carrier member has an upper abutment face extending substantially normal to said predetermined direction and engaging said roller from below.

Claim 5

A stapling machine as defined in claim 2, wherein said support means comprises an elongated guide member formed with an elongated groove extending in said predetermined direction and having a bottom face and a pair of side faces, one of which constitutes said guide face means, said driver member and said carrier member being constituted by a pair of elongated bars arranged superimposed upon each other in said groove and being reciprocable therein.

Claim 6

A stapling machine as defined in claim 4, wherein said bar constituting said dRiver has a rear face engaging the bottom face of said groove, and a front face, said bar constituting said carrier having a rear face engaging said front face of the other bar, said punches being carried on said rear face of said carrier bar on a portion thereof downwardly spaced from the bottom end of the driver bar, and including a cover fixed to said guide member extending over the open side of said slot and engaging the front face of said carrier bar.

Claim 7

A stapling machine as defined in claim 1, wherein said means for moving said retractable anvil to said retracted position comprises cooperating cam means on said anvil and on one of said punches.

Claim 8

A stapling machine as defined in claim 1, wherein said punch located between said die and said one side of said retractable anvil is formed in the face thereof facing said die with an elongated groove of V-shaped cross-section and wherein said die is provided with an elongated projection of corresponding V-shaped cross-section and projecting into said groove.

Claim 9

A stapling machine as defined in claim 7, and including mounting means mountind said die on said support means adjustable in a direction normal to said predetermined direction to reduce any clearance between said projection and said groove after grinding of said die projection.

Claim 10

A stapling machine as defined in claim 1, wherein each of said punches is provided on the face thereof facing the other punch with an elongated guide groove extending in said predetermined direction for guiding said clincher during its movement relative to said punches.

Claim 11

A stapling machine as defined in claim 1, wherein said driver is provided at the lower end thereof with a slot extending in said predetermined direction, said clincher having an upper portion located in said slot, and means engaging said upper portion of said clincher for releasably connecting said clincher to said driver.

Claim 12

A stapling machine as defined in claim 1, and including means for stepwise feeding a wire between said die and said punches during movement of said driver and said carrier therewith along the return stroke.

Claim 13

A stapling machine as defined in claim 11, wherein said feeding means comprises feed pawl means movable along a feed stroke for feeding said wire in one direction and a return stroke, a holding pawl means substantially preventing movement of said wire in the opposite direction during the return stroke of said feed pawl means, and cooperating means on said carrier and said feed pawl means for moving the latter along said feed stroke during movement of said carrier together with the driver during the return stroke of the latter.

Claim 14

A stapling machine as defined in claim 12, wherein said feed pawl means comprises a lever tiltably mounted between the ends thereof on said support means, and wherein said cooperating means comprise a cam face on said carrier and follower means connected to said lever and adapted to engage said cam face.

Claim 15

A stapling machine as defined in claim 13, and including biasing means engaging the lever and urging said follower toward said cam face, and means cooperating with said lever for adjusting the length of the return stroke and therewith also the length of the feeding stroke thereof.

Claim 16

A stapling machine as defined in claim 1, wherein said moving means comprise fluid actuated cylinder and piston means.

Claim 17

A stapling machine as defined in claim 15, wherein said fluid actuated cylinder and piston means comprise a cylinder mounted on said support means, a piston reciprocable in said cylinder means and having a piston rod connected to said driver, and control means for alternatingly feeding pressure fluid to opposite ends of said cylinder.

Claim 18

A stapling machine as defined in claim 16, wherein said control means comprises a solenoid operated valve and switch means connected to the solenoid of the valve for actuating the solenoid.

Claim 19

A stapling machine as defined in claim 1 wherein said additionAl biasing means comprises a compression spring in said slot between the lower end of the latter and said pin for urging said pin against the upper end of said slot.

Claim 20

A stapling machine comprising support means; combined bending and cutting means comprising a stationary die having a cutting edge and being mounted on said support means, a retractable anvil mounted on said support means spaced from said die and being movable between an active and a withdrawn position, a pair of spaced punches reciprocable in a predetermined direction, one of said punches having a cutting edge cooperating with said cutting edge of said die and being located between said die on one side of said anvil and the other of said punches being located on the other side of said anvil, said punches cooperating with said die and said anvil for cutting off a portion of a wire between said die and said punches, for then bending the cut-off wire portion into a U-shaped staple and for subsequently moving the U-shaped staple downwardly, means biasing said retractable anvil to said active position, and means for moving said anvil to said retracted position after the wire portion has been bent into a U-shaped staple; clinching means comprising a clinching anvil mounted on said support means downwardly spaced from said retractable anvil and a clincher located between and reciprocable in the same direction as said punches and cooperating with said clinching anvil for clinching the U-shaped staple; a carrier carrying said two punches spaced from each other; a driver mounted on said support means reciprocable in said predetermined direction and carrying said clincher for movement therewith; moving means connected to said driver for moving the same along an active stroke from an upper rest position to a lower end position in which said clincher clinches said U-shaped staple and along a return stroke back to said rest position; coupling means movable between a coupling position and an uncoupling position for connecting, when in said coupling position, said carrier to said driver for movement along said active stroke, said coupling means comprising a roller, a pair of abutment means respectively provided in said driver and said carrier to respectively engage said roller on opposite portions of its peripheral surface, and guide face means on said support means for maintaining said roller between said pair of abutment means; cooperating stop means on said support means and said carrier for stopping the movement of the latter after said punches mounted thereon have bent said cut-off wire portion into a U-shaped staple and moved the latter toward said clinching anvil; means cooperating with said coupling means after stopping of said carrier and further movement of said driver along its active stroke for moving said coupling means to said uncoupling position so as to permit said clincher carried by said driver to move downwardly relative to said punches to clinch the staple, said last-mentioned means comprising a cam face on one of said abutment means inclined to said predetermined direction in such a manner to push said roller toward said guide face means, and a pocket in said guide face means laterally aligned with said roller in the position the latter reaches when said carrier is stopped by said stop means so that the roller will move by the action of said cam face into said pocket and out of engagement with said abutment means on said carrier permitting thereby said driver to continue its movement while said carrier is stopped; and means to return said coupling means to said coupling position during movement of said driver along its return stroke, said returning means comprising a pusher member having an end face and being reciprocable in said pocket in a direction transverse to said predetermined direction between a first position in which said end face is flush with said guide face means and a second position withdrawn into said pocket for a distance equal to the diameter of said roller, and further Biasing means for biasing said pusher member to said first position.

Claim 21

A stapling machine comprising support means; combined bending and cutting means comprising a stationary die having a cutting edge and being mounted on said support means, a retractable anvil mounted on said support means spaced from said die and being movable between an active and a withdrawn position, a pair of spaced punches reciprocable in a predetermined direction, one of said punches having a cutting edge cooperating with said cutting edge of said die and being located between said die on one side of said anvil and the other of said punches being located on the other side of said anvil, said punches cooperating with said die and said anvil for cutting off a portion of a wire between said die and said punches, for then bending the cut-off wire portion into a U-shaped staple and for subsequently moving the U-shaped staple downwardly, means biasing said retractable anvil to said active position, and means for moving said anvil to said retracted position after the wire portion has been bent into a U-shaped staple; clinching means comprising a clinching anvil mounted on said support means downwardly spaced from said retractable anvil and a clincher located between and reciprocable in the same direction as said punches and cooperating with said clinching anvil for clinching the U-shaped staple; a carrier carrying said two punches spaced from each other; a driver mounted on said support means reciprocable in said predetermined direction and carrying said clincher for movement therewith; moving means connected to said driver for moving the same along an active stroke from an upper rest position to a lower end position in which said clincher clinches said U-shaped staple and along a return stroke back to said rest position; coupling means movable between a coupling position and an uncoupling position for connecting, when in said coupling position, said carrier to said driver for movement along said active stroke, said coupling means comprising a roller, a pair of abutment means respectively provided in said driver and said carrier to respectively engage said roller on opposite portions of its peripheral surface, and guide face means on said support means for maintaining said roller between said pair of abutment means; cooperating stop means on said support means and said carrier for stopping the movement of the latter after said punches mounted thereon have bent said cut-off wire portion into a U-shaped staple and moved the latter toward said clinching anvil; means cooperating with said coupling means after stopping of said carrier and further movement of said driver along its active stroke for moving said coupling means to said uncoupling position so as to permit said clincher carried by said driver to move downwardly relative to said punches to clinch the staple, said last-mentioned means comprising a cam face on one of said abutment means inclined to said predetermined direction in such a manner to push said roller toward said guide face means, and a pocket in said guide face means laterally aligned with said roller in the position the latter reaches when said carrier is stopped by said stop means so that the roller will move by the action of said cam face into said pocket and out of engagement with said abutment means on said carrier permitting thereby said driver to continue its movement while said carrier is stopped; and means to return said coupling means to said coupling position during movement of said driver along its return stroke, said returning means comprising a pusher member having an end face and being reciprocable in said pocket in a direction transverse to said predetermined direction between a first position in which said end face is flush with said guide face means and a second position withdrawn into said pocket for a distance equal to the diameter of said roller, and further Biasing means for biasing said pusher member to said first position.

Claim 22

A stapling machine comprising support means; combined bending and coupling means compring a stationary die having a cutting edge and being mounted on said support means, a retractable anvil mounted on said support means spaced from said die and being movable between an active and a withdrawn position, a pair of spaced punches reciprocable in a predetermined direction, one of said punches having a cutting edge cooperating with the cutting edge of said die and being located between said die and one side of said anvil, and the other being located on the other side of said anvil, said punches cooperating with said die and said anvil for cutting off a portion of a wire fed between said die and said punches, for then bending the cut-off wire portion into a U-shaped staple and for subsequently moving the U-shaped staple downwardly, means biasing said retractable anvil to said active position, and means for moving said anvil to said retracted position after the wire portion has been bent into a U-shaped staple; clinching means comprising a clinching anvil mounted on said support means downwardly spaced from said retractable anvil and a clincher located between and reciprocable in the same direction as said punches and cooperating with said clinching anvil for clinching the U-shaped staple; a carrier carrying said two punches spaced from each other; a driver mounted on said support means reciprocable in said predetermined direction and carrying said clincher for movement therewith; moving means connected to said driver for moving the same along an active stroke from an upper rest position to a lower end position in which said clincher clinches said U-shaped staple and along a return stroke back to said rest position; coupling means movable between a coupling position and an uncoupling position for connecting, when in said coupling position, said carrier to said driver for movement along said active stroke; cooperating stop means on said support means and said carrier for stopping the movement of the latter after said punches mounted thereon have bent said cut-off wire portion into a U-shaped staple and moved the latter toward said clinching anvil, said stop means comprising a member fixed to the upper end of said carrier projecting laterally therefrom and formed with a threaded bore therethrough, a stop screw adjustably screwed in said bore, and a stop face on said support means to be engaged by the end of said stop screw; means cooperating with said coupling means after stopping of said carrier and further movement of said driver along its active stroke for moving said coupling means to said uncoupling position so as to permit said clincher carried by said driver to move downwardly relative to said punches to clinch the staple; and means to return said coupling means to said coupling position during movement of said driver along its return stroke.

Claim 23

A stapling machine comprising support means; combined bending and coupling means compring a stationary die having a cutting edge and being mounted on said support means, a retractable anvil mounted on said support means spaced from said die and being movable between an active and a withdrawn position, a pair of spaced punches reciprocable in a predetermined direction, one of said punches having a cutting edge cooperating with the cutting edge of said die and being located between said die and one side of said anvil, and the other being located on the other side of said anvil, said punches cooperating with said die and said anvil for cutting off a portion of a wire fed between said die and said punches, for then bending the cut-off wire portion into a U-shaped staple and for subsequently moving the U-shaped staple downwardly, means biasing said retractable anvil to said active position, and means for moving said anvil to said retracted position after the wire portion has been bent into a U-shaped staple; clinching means comprising a clinching anvil mounted on said support means downwardly spaced from said retractable anvil and a clincher located between and reciprocable in the same direction as said punches and cooperating with said clinching anvil for clinching the U-shaped staple; a carrier carrying said two punches spaced from each other; a driver mounted on said support means reciprocable in said predetermined direction and carrying said clincher for movement therewith; moving means connected to said driver for moving the same along an active stroke from an upper rest position to a lower end position in which said clincher clinches said U-shaped staple and along a return stroke back to said rest position; coupling means movable between a coupling position and an uncoupling position for connecting, when in said coupling position, said carrier to said driver for movement along said active stroke; cooperating stop means on said support means and said carrier for stopping the movement of the latter after said punches mounted thereon have bent said cut-off wire portion into a U-shaped staple and moved the latter toward said clinching anvil, said stop means comprising a member fixed to the upper end of said carrier projecting laterally therefrom and formed with a threaded bore therethrough, a stop screw adjustably screwed in said bore, and a stop face on said support means to be engaged by the end of said stop screw; means cooperating with said coupling means after stopping of said carrier and further movement of said driver along its active stroke for moving said coupling means to said uncoupling position so as to permit said clincher carried by said driver to move downwardly relative to said punches to clinch the staple; and means to return said coupling means to said coupling position during movement of said driver along its return stroke.

Claim 24

A stapling machine comprising support means; combined bending and cutting means comprising a stationary die having a cutting edge and being mounted on said support means, a retractable anvil mounted on said support means spaced from said die and being movable between an active and a withdrawn position, a pair of spaced punches reciprocable in a predetermined direction, one of said punches having a cutting edge cooperating with the cutting edge of said die and being located between said die and one side of said anvil, and the other being located on the other side of said anvil, said punches cooperating with said die and said anvil for cutting off a portion of a wire fed between said die and said punches, for then bending the cut-off wire portion into a U-shaped staple and for subsequently moving the U-shaped staple downwardly, means biasing said retractable anvil to said active position, and means for moving said anvil to said retracted position after the wire portion has been bent into a U-shaped staple; clinching means comprising a clinchiNg anvil mounted on said support means downwardly spaced from said retractable anvil and a clincher located between and reciprocable in the same direction as said punches and cooperating with said clinching anvil for clinching the U-shaped staple; a carrier carrying said two punches spaced from each other; a driver mounted on said support means reciprocable in said predetermined direction and carrying said clincher for movement therewith; moving means connected to said driver for moving the same along an active stroke from an upper rest position to a lower end position in which said clincher clinches said U-shaped staple and along a return stroke back to said rest position, said driver and said carrier being constituted by a pair of elongated bars reciprocable in said predetermined direction and each being formed with a bore extending transverse to said predetermined direction, the bores being aligned with each other at least in said rest position of said driver; cooperating stop means on said support means and said carrier for stopping said movement of the latter after said punches mounted thereon have bent said cut-off wire into a U-shaped staple and moved the latter towards said clinching anvil; coupling means movable between a coupling position and an uncoupling position for connecting, when in said coupling position, said carrier to said driver for movement along said active stroke, said coupling means comprising a pin extending through said bores in said aligned position of the latter, second biasing means cooperating with said pin for biasing said latter in said transverse direction for moving said pin out of the bore of one of said bars, means cooperating with said pin for rendering said second biasing means inactive during the active stroke of said driver until the carrier is stopped by said stop means and for rendering said second biasing means active when said carrier is stopped to thus move said pin out of the bore in said one bar permitting thereby said driver to continue its movement while said carrier is stopped so as to permit said clincher carried by said driver to move downwardly relative to said punches to clinch the staple; and means to return said coupling means to said coupling position during movement of said driver along its return stroke.

Claim 25

A stapling machine comprising support means; combined bending and cutting means comprising a stationary die having a cutting edge and being mounted on said support means, a retractable anvil mounted on said support means spaced from said die and being movable between an active and a withdrawn position, a pair of spaced punches reciprocable in a predetermined direction, one of said punches having a cutting edge cooperating with the cutting edge of said die and being located between said die and one side of said anvil, and the other being located on the other side of said anvil, said punches cooperating with said die and said anvil for cutting off a portion of a wire fed between said die and said punches, for then bending the cut-off wire portion into a U-shaped staple and for subsequently moving the U-shaped staple downwardly, means biasing said retractable anvil to said active position, and means for moving said anvil to said retracted position after the wire portion has been bent into a U-shaped staple; clinching means comprising a clinchiNg anvil mounted on said support means downwardly spaced from said retractable anvil and a clincher located between and reciprocable in the same direction as said punches and cooperating with said clinching anvil for clinching the U-shaped staple; a carrier carrying said two punches spaced from each other; a driver mounted on said support means reciprocable in said predetermined direction and carrying said clincher for movement therewith; moving means connected to said driver for moving the same along an active stroke from an upper rest position to a lower end position in which said clincher clinches said U-shaped staple and along a return stroke back to said rest position, said driver and said carrier being constituted by a pair of elongated bars reciprocable in said predetermined direction and each being formed with a bore extending transverse to said predetermined direction, the bores being aligned with each other at least in said rest position of said driver; cooperating stop means on said support means and said carrier for stopping said movement of the latter after said punches mounted thereon have bent said cut-off wire into a U-shaped staple and moved the latter towards said clinching anvil; coupling means movable between a coupling position and an uncoupling position for connecting, when in said coupling position, said carrier to said driver for movement along said active stroke, said coupling means comprising a pin extending through said bores in said aligned position of the latter, second biasing means cooperating with said pin for biasing said latter in said transverse direction for moving said pin out of the bore of one of said bars, means cooperating with said pin for rendering said second biasing means inactive during the active stroke of said driver until the carrier is stopped by said stop means and for rendering said second biasing means active when said carrier is stopped to thus move said pin out of the bore in said one bar permitting thereby said driver to continue its movement while said carrier is stopped so as to permit said clincher carried by said driver to move downwardly relative to said punches to clinch the staple; and means to return said coupling means to said coupling position during movement of said driver along its return stroke.

Claim 26

A stapling machine as defined in claim 21, wherein said support means comprises an elongated guide member formed with an elongated groove extending in said predetermined direction and having a bottom face and a pair of side faces, said elongated bars being arranged superimposed upon each other in said groove and said bores having axes substantially normal to said bottom face of said groove.

Claim 27

A stapling machine as defined in claim 22, wherein said second biasing means comprises spring means engaging said pin and being biased for urging said pin out of the bore of said one bar, and wherein said means for rendering said second biasing means inactive and active comprises stationary cam means having a cam face engaging one end of said pin, said cam face having an elongated portion extending in said predetermined direction substantially parallel to said bottom face of said groove and a portion inclined to said elongated portion in a direction so as to permit said pin to move under the influence of said spring means out of said bore in said one bar.

Claim 28

A stapling machine as defined in claim 23, wherein said means for returning said coupling means to said coupling position comprises means to align said bores with each other during the return stroke of said driver so that said cam means may move said pin against the action of said second biasing means back into the bore of said one bar.

Claim 29

A stapling machine as defined in claim 24, wherein said aligning means comprises an elongated slot extending on said predetermined direction and being formed in one of said bars, a pin member fixed to the other bar and extending into said slot, and additional biasing means cooperating with said bars for yiEldably maintaining said pin member in engagement with one end of said slot, said one end of said slot in said one bar and said pin member in said other bar being arranged relative to said bores so that the latter are aligned with each other when said pin member engages said one end of said slot.

Claim 30

A stapling machine as defined in claim 25, wherein said additional biasing means comprises a coil spring located in said slot and connected at opposite ends to said driver and said carrier, respectively.

Claim 31

A stapling machine as defined in claim 23, wherein said driver has a rear face engaging said bottom face of said groove and a front face, said carrier being superimposed on said driver and having a rear face engaging said front face of said driver and a front face, said one bar being constituted by said driver.

Claim 32

A stapling machine as defined in claim 27, and including a cover fixed to said guide member extending over the open side of said groove and engaging with one face thereof said one face of said carrier, said cover being formed with an elongated slot extending in said predetermined direction, said pin having an end portion projecting into said slot in said cover, said cam being fixed to said cover extending over said slot formed therein.

Claim 33

A stapling machine as defined in claim 28, wherein said pin has at the free end of the portion extending into said slot of said cover a head of larger diameter than the remainder of said pin and having a spherical face engaging said cam face, and wherein said spring means comprises a coil compression spring about said portion of said pin between the head and the front face of said carrier.

Claim 34

In a stapling machine or the like, a combination comprising guide means formed with an elongated groove; an elongated driver member and an elongated driven member mounted superimposed upon each other in said groove for movement in longitudinal direction along an active stroke and a return stroke; coupling means movable between a coupling position and an uncoupling position for connecting, when in said coupling position, said driver member to said driven member for movement along its strokes; stop means cooperating with said driven member for stopping movement of the latter before said driver member reaches the end of its active stroke; means cooperating with said coupling means for moving the same to said uncoupling position when movement of the driven member has been stopped while said driver member finishes its active stroke; means to return said coupling means to said coupling position during movement of said driver member along its return stroke; and additional means between said driven member and said driver member for moving said driven member with said driver member during said return stroke while positioning said driven member relative to said driver member for permitting movement of said coupling means to said coupling position, said additional means comprising an elongated slot formed in one of said members, a pin fixed to the other of said members and biasing means for yieldably maintaining said pin in engagement with one end of said slot.

Claim 35

In a stapling machine or the like, a combination comprising guide means formed with an elongated groove; an elongated driver member and an elongated driven member mounted superimposed upon each other in said groove for movement in longitudinal direction along an active stroke and a return stroke; coupling means movable between a coupling position and an uncoupling position for connecting, when in said coupling position, said driver member to said driven member for movement along its strokes; stop means cooperating with said driven member for stopping movement of the latter before said driver member reaches the end of its active stroke; means cooperating with said coupling means for moving the same to said uncoupling position when movement of the driven member has been stopped while said driver member finishes its active stroke; means to return said coupling means to said coupling position during movement of said driver member along its return stroke; and additional means between said driven member and said driver member for moving said driven member with said driver member during said return stroke while positioning said driven member relative to said driver member for permitting movement of said coupling means to said coupling position, said additional means comprising an elongated slot formed in one of said members, a pin fixed to the other of said members and biasing means for yieldably maintaining said pin in engagement with one end of said slot.