Printing Mechanism

Abstract

An improved printer including striking means positioned within striking distance of a rotatable print drum, camming means for oscillating the striking means in a swing arc less than the striking distance between the print drum and striking means, and regulating means for causing the striking means to strike the print drum for printing contact therewith. The striking means is provided with one axis of oscillation at a non-printing time and a second axis of oscillation at printing time.

Description

BACKGROUND OF THE INVENTION

This invention relates to an improved compact printing mechanism of the type utilized in electronic desk calculators and other numerical read out devices. More particularly, this invention relates to a printer which generates little or no noise at printing time.

Conventional printing mechanisms employ a high speed ratchet rotor to impel a print hammer against a rotating print drum and the impulsive engagement of the ratchet with the print hammer generates a great deal of noise. Moreover, such printing mechanisms are usually complex, insufficiently durable and difficult to maintain.

Accordingly, the improved printing mechanism of this invention includes a minimum number of interengaging and moving parts and is substantially noiseless during the operation thereof.

SUMMARY OF THE INVENTION

Generally speaking, in accordance with the invention, a rotatable print drum arranged for receiving an array of print characters on the peripheral surface thereof is positioned within striking distance of a striking means for selectively striking the print drum and carrying a printable material interposed between the print drum and striking means into printing contact with the peripheral surface of the print drum. The striking means is provided with an interiorly slotted mid portion defined by a continuous interior edge thereof for receiving a camming means therein. Camming means for oscillating the striking means in a swing arc less than the striking distance between the peripheral surface of the print drum is provided and the striking means engage at least a portion of the continuous interior edge defining the interiorly slotted mid portion of the striking means and regulating means are provided for causing the striking means to strike and engage the peripheral surface of the print drum for printing contact therewith for selected periods of time.

When not in printing contact with the print drum, the striking means is provided with a first axis of oscillation. Upon being driven into printing contact with the print drum by the action of the regulating means, the striking means is provided with a second axis of oscillation. However, while in printing contact with the print drum, the striking means undergoes little or no oscillation whereby a clear, concise character is striken in the printable material interposed between the striking means and print drum. Therefore, a principal advantage of the improved printing mechanism of this invention is the elimination of smudged printing during the operation thereof. Additionally, the printable material, usually paper, on which printing occurs is not ripped during the printing process. Further, the noise which usually occurs during the printing process is substantially reduced since this improved printing mechanism does not utilize a high speed ratchet rotor as an element thereof.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a semi-schematic representation of one type of printing mechanism constructed in accordance with the invention; and

FIG. 2 is a semi-schematic representation of another striking means embodiment which may be used in connection with the improved printing mechanism of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, print drum 1 has an array of print characters spaced apart on the peripheral surface thereof and is mounted for rotation on a print drum shaft. Striking means 2 provided with a print hammer portion 5 thereof opposing print drum 1 and having an engaging tooth 4 at the opposite end thereof is positioned adjacent print drum 1 for selectively striking print drum 1 under the action of regulating means 8, hereinafter described in detail.

Oval slot 3 is interiorly defined in the mid portion of striking means 2 wherein camming means 7, preferably an eccentric cam, is received and engages at least a portion of the continuous interior edge defining interior slot 3 of striking means 2. Striking means 2 is further provided with guide groove 6 opposed to print hammer portion 5 for receiving stopper 10 for limiting the oscillatory movement of striking means 2 along a first axis of oscillation, hereafter described. Striking means 2 is normally biased against stopper 10 by the action of spring bias 11 thereon, one end of spring bias 11 being connected to striking means 2 and the other end thereof being connected to a fixed mounting. As striking means 2 strikes print drum 1, under the influence of regulating means 8, ink ribbon 16 engages printable material 15, for instance, a paper web, and both ink ribbon 16 and printable material 15 are sandwiched between print hammer 5 and print drum 1 whereby a print character is formed and inked on printable material 15.

Regulating means 8 includes a pair of lever arms, one arm terminating in integrally formed pawl 9 arranged for engaging tooth 4 of striking means 2 for causing the print hammer portion 5 of striking means 2 to strike and engage the peripheral surface of print drum 1 for printing contact therewith. The other lever arm of regulating means 8 is provided with an electro-conductive material responsive to the electrical impulses generated by solenoid 13. The trigger member or regulating means 8 including the lever arms and pawl 9 is pivotably mounted on trigger shaft 14 proximate striking means 2. Spring bias 12 connected at one end to a nub extension of the trigger lever and at its other end to a fixed mounting normally biases the trigger lever out of engagement with tooth 4 of striking means 2 and against stopper 19. When solenoid 13 is activated an electromagnetic field is provided thereby and the electro-conductive lever arm of the trigger member is attracted thereto whereby pawl 9 of the other lever arm of the trigger member engages tooth 4 of striking means 2 urging it uppwardly and outwardly thereby causing print hammer portion 5 to strike print drum 1 and sandwich printable material 15 and ink ribbon 16 therebetween.

In an operational but non-printing interval, eccentric cam 7 continuously rotates in the direction of the arrow shown in FIG. 1 whereby tooth 4 of striking means 2 oscillates between phantom positions 4' and 4", as shown in FIG. 1, while the innermost defining edge of guide groove 6 constantly engages stopper 10 for pivoting striking means 2 therearound and thereby providing a first axis of oscillation for striking means 2 when in a non-printing condition. When solenoid 13 is actuated thereby causing pawl 9 to engage tooth 4 of striking means 2 causing print hammer 5 to strike print drum 1, striking means 2 may undergo some slight oscillation under the influence of eccentric cam 7 and the line of inter-engagement between pawl 9 and tooth 4 become the axis of oscillation therefor whereby striking means 2 is provided with a second axis of oscillation which occurs during printing intervals thereof. However, during a printing interval, substantially no oscillation occurs because print drum 1 and eccentric cam 7 are synchronized in movement and as eccentric cam 7 urges tooth 4 counter-clockwise pawl 9 continues to bias against tooth 4 to maintain print hammer portion 5 in striking position against print drum 1. The sequence of operation is such that printing terminates as eccentric cam 7 urges tooth 4 into position 4" and tooth 4 is simultaneously released by pawl 9 through the deactivation of solenoid 13 whereby the trigger lever of regulating means 8 reassumes its normally biased position against stopper 19. For instance, when print drum 1 rotates X times per minute eccentric cam 7 rotates NX times per minute, and solenoid 13 will activate pawl 9 for causing print hammer portion 5 to strike print drum 1 at 1/NX.

Referring now to FIG. 2, wherein an alternate striking means embodiment 2' is shown, legs 17 and 18 of striking means 2' are elastically deformable and securely engage eccentric cam 7 as it rotates in slot 3. By providing striking means 2' with elastically deformable legs which securely engage eccentric cam 7 even after long periods of use a more uniform printing pressure of print hammer portion 5 against print drum 1 is achieved during printing intervals.

It will thus be seen that the advantages set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting scope.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims

I claim:

1. A printer comprising a rotatable print drum having an array of print characters on the peripheral surface thereof, oscillatable striking means for selectively striking said print drum for carrying a printable material interposed therebetween into printing contact with said peripheral surface of said print drum, said striking means comprising a reciprocable print hammer having a print face arranged opposite a predetermined portion of said print drum and within striking distance thereof, a stopper guide groove substantially opposite said print hammer face and extending substantially laterally a predetermined distance toward said print face, an interior cam slot substantially perpendicular to said print face and stopper guide groove, and a tooth remote from said print hammer depending downwardly from said striking means; a stopper engageable in said stopper guide groove for limiting a reciprocal return stroke of said print hammer after an imprint is effected, said stopper being fixed relative to the reciprocable movement of said print hammer; means for normally biasing said print hammer against said stopper; a rotatable eccentric cam mounted in said interior cam slot, said cam being unidirectionally rotatable counter to the print stroke direction of said reciprocable print hammer, said cam being arranged to oscillate said striking means about said stopper in a nonprint position of said printer; an impulse responsive trigger lever engageable with said tooth of said striking means for driving said print hammer of said striking means into printing contact with said print drum; biasing means for normally biasing said trigger lever out of engagement with said tooth of said striking means; and means for generating an impulse to which said trigger lever is responsive for driving said trigger lever oppositely of said normal bias thereon for driving said print hammer; said striking means being oscillatable about a point of contact between said trigger lever and said tooth of said striking means in a print position of said printer and said print hammer thereof being simultaneously reciprocable between said print drum and said stopper.