US3187668A - Hammer suspension for high speed printer - Google Patents

Description

June 1955 L. w. MARSH, JR 3,137,668

HAMMER SUSPENSION FOR HIGH SPEED PRINTER Filed June 27, 1963 FIG. I

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LYNN W. MARSH, JR.

ATTORNEYS United States Patent 3,187,668 HAMMER SUSPENSIGN FDR HIaGH SPEED PREITER Lynn W. Marsh, In, Marblehead, Mass assignor to ANelex Corporation, Boston, Mass., a corporation of New Hampshire Filed .l'une 27, 1963, Ser. No. 291,012 4 Claims. (Cl. 101-93) This invention relates to an improved hammer suspension for high speed printers of a type generally disclosed and claimed in U. S. Patent No. 2,940,385 to Frank R. House, entitled High Speed Printer, issued June 14, 1960, and assigned to the assignee of the present application.

The above patent describes a high speed printer of a type having a rotatable print wheel with a series of characters circumferentially spaced thereabout, together with a series of hammers mounted in radial juxtaposition to the periphery of the wheel for actuation by electrical impulses to imprint a desired series of characters on paper passing intermediate the print wheel and hammer. According to the patent, the hammers are pivotally mounted by means of individual reed springs, so as to be actuable by solenoid devices. However, it has been found in practice that the hammers tend to oscillate after actuation, and may strike the paper against the print wheel more than once as the hammer oscillates. This may smear the paper, or produce a second ghost impression on the rebound. For this reason, external damping may be necessary, and takes the form of return springs, according to the aforementioned patent. However, these return springs are slidably engaged withthe hammer, and introduce friction into the suspension. They quickly Wear the hammer because of the high frequency of actuation to which it is subjected. Furthermore, this type of suspension is subject to fatigue after a period of use.

It is the principal object of the present invention to provide an improved hammer suspension for a high speed printer, which is frictionless and therefore free of wear from this cause. The improved suspension features internal spring return and damping action. It is a further object of the invention to provide an improved hammer suspension which is less subject to fatigue. Another object is to provide internal damping of hammer oscillation, to prevent rebounding impact with the print wheel following release of the hammer. It is a further object of the invention to provide a hammer suspension with pro-stressing means for causing the suspension to oscillate about a position other than its neutral position, thereby to prevent rebound into a print wheel. Further objects and advantages of the invention will become apparent as the following description proceeds.

Briefly stated, according to a preferred embodiment thereof, 1 may carry out my invention by supporting a hammer block in the free end of a first flexible beam whose opposite end is fixed in a stationary block, mounting an actuating block in the free end ofa second flexible beam whose opposite end is fixed in the stationary block, and fixing the opposite ends of still a third flexible beam in the hammer block and actuating block, to form in eifect a parallel spring linkage supporting the hammer and actuating blocks from the stationary block. The first and second beams are substantially coaxial, and both are parallel to the third beam. The dimensions and flexural characteristics of the three beams are selected to give a desired spring rate to the entire suspension system, and desired damping characteristics. The natural frequencies of the three beams being unequal, the system affords natural damping of oscillation. Upon the application of a deflecting force to the actuating block, the beams flex according to the composite characteristic of the linkage to deflect the hammer block in an opposite sense, into abutment with the print wheel. Upon release of the actuating block, the return of the hammer to the neutral position is governed by the composite damping characteristics of the beams.

The system may be pre-stressed so that oscillation of the hammer takes place about the pre-stressed position rather than about a neutral position, and rebounding of the hammer into the print wheel may be prevented in this fashion; In a preferred form, either the beams has adjustable connection with one of the hammer or actuating block, so that its effective length may be adjusted to pre-stress that particular beam in tension or compression. The system will then oscillate about the pre-stressed position, rather than about the neutral position, of the spring lever system. Preferably, the beams are tubular in form to permit .pre-stressing with a minimum of fatigue. The pre-stressing adjustment can also be utilized to insure that the face of the hammer is square with the print wheel characters at the point of impact. If additional damping is required, a further beam may be cantilevered in one or the other of the hammer and actuating blocks, and received in a stationary external slide so as to dampen the oscillation of the suspension linkage without interfering with its flexure.

While the specification concludes with claims particularly pointing out the subject matter which I regard as my invention, it i believed that a clearer understanding may be gained from the following detailed description of preferred embodiments thereof, referring to the accompanying drawings, in which:

FIG. 1 is a view in elevation showing a preferred form of the improved suspension in an undeflected condition;

FIG. 2 is a sectional view taken along line 22 in FIG. 1, looking in the direction of the arrows;

FIG. 3 is a schematic view in elevation showing the suspension of FIG. 1 in a pre-stressed condition;

FIG. 4 i a view similar to FIG. 3, but showing the suspension deflected in a manner to actuate the hammer; and

FIGS. 5-7 are schematic views in elevation showing various modifications in which external damping is applied to the suspension system.

Referring to FIGS. 1-2, a preferred construction is shown in operative relation to a rotatable print wheel 2 having spaced about its periphery a serie of raised characters 3. The suspension serves to support a hammer block 4 in radially spacedrelation to the print wheel, so that the hammer block may be driven against the characters 3 to print them upon a moving sheet of paper 5 by means of a carbon sheet 6, all as generally described in the aforementioned House Patent No. 2,940,385.

In the preferred form, the suspension is supported in a stationary block 7 mounted upon a base member 8, and includes a first flexible beam 11 and a second flexible beam 12 which are substantially coaxial and cantilevered in the block 7, and aflixed at their free ends to the hammer block 4 and to an L-shaped actuating block 14, respectively. The hammer block 4 and actuating block 14 are further interconnected by a third flexible beam 15, substantially parallel to both the first and second beams, to form a parallel spring linkage. According to a feature of the invention, the effective length of the beam 15 may be adjusted to pro-stress the suspension, by means of a knurled nut 17 threaded on a reduced end portion 18 of the beam 15, which is slidably received through the hammer block 4 for this purpose. By these means, the suspension may be variably pre-stressed, as is illustrated in FIG. 3.

In the preferred form, the beams 11, 12 and 15 are tubular in form, to permit pre-stressing with a minimum of fatigue. While the dimensions and spring constants of the various beams may be selected to give desired deflection and damping characteristics, the beam 15 is relatively stiff in the form shown, While the beam 11 is designed to be somewhat more flexible than the beam 12. The differing natural frequencies of vibration of the various beams provide internal damping action. To actuate the hammer into impact with the print wheel, a solenoid is provided, comprising a coil 29 and a core structure 22, which is of ferromagnetic material, as is the block 14. Application of current to the coil applies a downward force to the block 14 as shown at F in FIG. 4, which deflects the suspension as shown by that figure, driving the hammer block upwardly into contact with the print Wheel. Subsequent release of the actuating force permits the beams to return the hammer to its initial position by a spring action, with an oscillation-damping characteristic which depends upon the individual characteristicsof the beams 11, 12 and 15. With the suspension pre-stressed as shown in FIG. 3, the suspension will oscillate about this position, rather than about the neutral position of FIG. 1, with the result that the hammer block may be prevented from striking the print wheel on rebound, and thereby avoid forming ghost impressions, and smearing of the paper by the carbon.

Referring to FIGURES 5,. 6 and 7, modified forms are shown in which additional damping and spring action is alforded by aflixing an additional flexible beam 24 in either of the blocks 4 or 14, extending coaxially with either the beam 15 or the beams 11 and 12. The free end of the beam 24 is slidably received by a slideway 26 in a stationarysupport member 28, so that the beam 24 accepts torsional moments applied by flexure of the suspension, but is longitudinally free so as not to interfere with the desired flexural movement. It will be apparent that by proper selection of the dimensions and spring constants of the various beams, desired composite damping and flexing characteristics may be secured.

While preferred embodiments of the improved hammer suspension have been described by way of illustration, it

will be apparent to those skilled in the art that various changes and modifications may be made Without departing from the true spirit and scope of the invention, which I therefore intend to define in the appended claims without limitation to the details of the foregoing embodiments.

What I claim is;

1. In a high speed printer, a print wheel and a hammer block constructed and arranged for impacting said print wheel, a flexible suspension for said hammer block comprising a stationary base member, a freely movable actuating block, a first flexible beam cantilevered at one end thereof in said base member, extending in one direction therefrom, and atfixed at an opposite end thereof in said hammer block, a second flexible beam substantially c0- axial with said first beam and cantilevered at one end thereof in said base member, said second, beam extending in an opposite'direction than said first beam from said base member, and aflixed at an opposite end thereof in said actuating block, and a third flexible beam affixed at opposite ends thereof in said hammer blockand said actuating block, said first and second beams extending generally parallel to said'third beam to form a deflectable suspension flexibly supporting said hammer block and said actuating block on said base member, means for releasably moving said actuating block in a direction transverse to the parallel extent of said beams, for effecting oscillatory displacement of said hammer block into engagement with said print wheel upon movement and subsequent release of said actuating block.

2. The combination recited in claim 1, in which at least one of said beams is adjustably affixed in one of said blocks for adjustment of the effective length of said one beam, whereby said suspension may be pre-stressed to a flexed position about which said suspension oscillates when deflected and subsequently released.

3. The combination recited in claim 1, together with at least one further flexible beam cantilevered at one end thereof in one of said blocks, said further beam being slidably received in said stationary base member for restraint against bending moments applied by flexure of said suspension. V

4. The combination recited in claim 1, in which said beams have different flexural characteristics to afford internal damping of vibration of the suspension.

References Cited by the Examiner UNITED STATES PATENTS 3,041,964 7/62 Simpsonet al. 3,072,045 1/63 Goin.

WILLIAM B. PENN, Primary Examiner.

Claims (1)

1. IN A HIGH SPEED PRINTER, A PRINT WHEEL AND A HAMMER BLOCK CONSTRUCTED AND ARRANGED FOR IMPACTING SAID PRINT WHEEL, A FLEXIBLE SUSPENSION FOR SAID HAMMER BLOCK COMPRISING A STATIONARY BASE MEMBER, A FREELY MOVABLE ACTUATING BLOCK, A FIRST FLEXIBLE BEAM CANTILEVERED AT ONE END THEREOF IN SAID BASE MEMBER, EXTENDING IN ONE DIRECTION THEREFROM, AND AFFIXED AT AN OPPOSITE END THEREOF IN SAID HAMMER BLOCK, A SECOND FLEXIBLE BEAM SUBSTANTIALLY COAXIAL WITH SAID FIRST BEAM AND CANTILEVERED AT ONE END THEREOF IN SAID BASE MEMBER, SAID SECOND BEAM EXTENDING IN AN OPPOSITE DIRECTION THAN SAID FIRST BEAM FROM SAID BASE MEMBER, AND AFFIXED AT AN OPPOSITE END THEREOF IN SAID ACTUATING BLOCK, AND A THIRD FLEXIBLE BEAM AFFIXED AT OPPOSITE ENDS THEREOF IN SAID HAMMER BLOCK AND SAID ACTUATING BLOCK, SAID FIRST AND SECOND BEAMS EXTENDING

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