Resiliently mounted drive nut and carriage assembly

In a high speed printer wherein a print head is reciprocably driven back and forth along a linear path in close proximity to a print medium which engages and is driven by a rotatably controlled platen, and wherein a reversible inked ribbon interposed between the print head and the print medium transfers character images to and imprints them on said medium in a line-by-line manner while the print medium is drawn taut against the platen, said combination further comprising:

• a rotatably driven lead screw;
• guide means including at least one elongated guide rod;
• a carriage mountable on and slidably movable along at least said one guide rod positioned parallel to said lead screw, said carriage having at least one side wall with an over-sized aperture formed therein and through which said lead screw axially passes without contact;
• a drive nut mountable on said driven lead screw for linear translational movement therealong, said drive nut comprising an elongated body portion having a first threaded bore extending axially a predetermined distance inwardly from one end thereof, and a second unthreaded bore extending axially inwardly from the other end thereof and merging with said first threaded bore along an intermediate region of said drive nut, said second unthreaded bore having a diameter larger than the diameter of said lead screw so that said body is skewable slightly relative to the axis of said lead screw, and a peripheral groove formed near said other end of said drive nut;
• resilient mounting means including a resilient O-ring dimensioned so that an inner annular portion thereof is seated under compressive force in said peripheral groove of said drive nut, said O-ring having an outer annular portion which is partially seated within an undercut groove formed in the peripheral edge of said aperture in said carriage side wall, said undercut groove being exposed at least to one side surface of said side wall, and the width of said O-ring being sufficient so that said O-ring protrudes outwardly a predetermined distance from said one side wall surface;
• and
• first and second clamping plates, each having an over-sized central aperture through which said lead screw axially passes without contact, said first clamping plate having one side surface thereof biased firmly against an adjacent side surface of said apertured carriage side wall, with an annular portion of one side surface of said second clamping plate, surrounding said aperture therein, being resiliently biased in an adjustable manner against at least an annular portion of an outwardly protruding side surface of said O-ring so as to establish a controllable space therebetween, while resiliently securing said O-ring to said carriage side wall, the compressive force exerted on said O-ring by said clamping plates thereby determining, in part, the degree of resiliency exhibited by said O-ring in mounting said drive nut from said other body end, in a cantilevered manner, on said carriage, the axis of said drive nut being thereby slightly skewable relative to the axis of said lead screw, the O-ring minimizing any relative axial or radial displacement between said drive nut and lead screw axes, as well as between said drive nut and carriage side wall, and wherein said O-ring is made out of a plastic material exhibiting a viscoelastic characteristic so that any kinetic energy-imparted forces applied thereto by said carriage are at least substantially absorbed and dissipated in the form of heat.

A lead screw driven, resiliently mounted drive nut and carriage assembly comprising:

• a rotatably driven lead screw;
• a carriage mountable on and slidably movable along at least one guide rod positioned parallel to said lead screw, said carriage having at least one side wall with an over-sized aperture formed therein and through which said lead screw axially passes;
• a drive nut mountable on said driven lead screw for linear translational movement therealong, said drive nut comprising an elongated body portion having a first threaded bore extending axially a predetermined distance inwardly from one end thereof, and a second unthreaded bore extending axially inwardly from the other end thereof and merging with said first threaded bore along an intermediate region of said drive nut, said second unthreaded bore having a diameter larger than the diameter of said lead screw so as to define an annular space therebetween, and a peripheral groove formed near said other end of said drive nut;
• and
• resilient mounting means including a resilient O-ring dimensioned so that an inner annular portion thereof is seated under compressive force in said peripheral groove of said drive nut, said O-ring having an outer annular portion which is partially seated within an undercut groove formed in the peripheral edge of said aperture in said carriage side wall, the width of said O-ring being dimensioned so as to protrude outwardly a predetermined distance from at least one surface of said carriage side wall, and said mounting means further including:
• means for compressively clamping said O-ring to said carriage side wall such that said O-ring resiliently mounts said drive nut from said other body end, in a cantilevered manner, on said carriage, the axis of said drive nut thereby slightly skewable relative to the axis of said lead screw, the O-ring minimizing any relative axial or radial displacement therebetween, as well as between said drive nut and carriage.