CA1181989A - Actuator mechanism for a printer or the like - Google Patents

Abstract

ACTUATOR MECHANISM FOR A PRINTER OR THE LIKE

Abstract An actuator element having a fixed end and a magne-tizable deflection end is releasably held in spring loaded condition at a non-operative positon by an electromagnetic operator means. In the preferred form, the actuator element is an elastic beam of magnetically permeable material. The operator means comprises first and second permanent magnets for generating separate magnetic fields of the same polarity proximate the magnetizable deflection end of the actuator element and magnetic core means combined with the permanent magnets to form at least first and second magnetic holding circuits with the deflection end of the actuator element through a common return path. A winding on the return path of the core means when energized generates flux in opposition to the flux from the permanent magnets to release the actuator element for movement to an operative position. Upon de-energization of the winding, the deflection end or the actuator element is retracted and held by the permanent magnets in spring loaded condition.

Description

ACTUATOR MECHANISM F~R A PRINTER OR THE LIKE

Description Technical Field This invention relates to actuator mechanisms and particu-larly to electromagnetic print hammers of the stored energy type also referred to as no-work print hammers. This in-vention has utility in related Canadian application of W.D.
Thorne titled "Band and Hammer Dot ~atrix Printer", Serial No. 371,788 flled February 26, 1981.

In the operation of electromagnetically operated print hammers, it is important that the hammer element, such as a lea~ spring, be capable of repeatedly moving from the stored energy position to the impact position and re-turn in a very short cycle time if printing is to occur at relatively high speeds. It is also important that the electromagnetic operating structure which retracts holds and releases the spring loaded hammer element be highly efficient and simple in structure so that power utilization is minimal and manu-facturing costs are kept at a minimum without sacrificing performance and reliability. It is also desirable that the electromagnetic sturcture be adaptable for multiple hammer assembly in which the hammer elements are independently adjustable to compensate for individual hammer flight time variations.

In U.S. Patent 4,189,997 issued February 26, 1980 a perma-nent magnet is embedded in a non-magnetic hammer head carried on the end of fle~ure springs. The hammer head is held in sprin~ loaded condition by the magnetic interaction of the permanellt magnet with a stationary electromagnet whose windin~ :is energized to release the hammer head for printing.

In U.S. Patent 4,200,043 an electromagnet is embedded in the hammer head. The hammer head is held in spring loaded condition by a pair of permanent magnets of opposite polarity. The electromagnet winding is energized through conductive flexure wires supporting the hammer to counteract the flux from the permanent magnlets.

In U.S. Patents 3,659,238, 3/656~425 and 3,941,052 magnetic armatures are carried on the end of a flexure element. A
permanent magnet is connected in a magnetic holding circuit with pole pieces configured to extend proximate the armature. A winding on a pole piece when energized bucks out flux from the permanent magnet to release the armature.
Patent 3,659,238 has a flux path for shunting buck out flux to prevent reverse magnetization of the permanent magnet.

U.S~ Patent 4,044,668 discloses a multiple hammer assembly having a magnetic circuit structure including an elongate permanent bar magnet magnetically coupled through a magnetic insert through the fixed end of resilient magnetic hammer elements. A magnetic plate is coupled to the permanent magnet to provide a common return path for individual coil wound pole pieces acting on the deflection end of the hammer elements. The magnetic circuit structure uses dummy end positions beyond the last hammer position to compensate for decreased field strength of the permanent magnet. A front plate of a hammer housing is made of magnetic material to form a parallel flux path with the hammer elements to increase the flux density in the deflection end of the hammer elements to the pole pieces.

U.S. Patent 3,906,85~ shows a control mechanism for plural spring loaded hammers which includes individual magnetic circuits in combination with a flux producing element. Each magnetic circuit includes a hammer hold portion and a control portion connected in parallel and each having a permanent magnet. A control coil on the control portion is energized to reverse the polarity of the control magnet to reduce the net amount of flux in the hold portion of the circuit. The coil is reverse energized to restore the control permanent magnet to the initial polarity for holding the hammer element.

Disclosure Of The Invention ~ .

~ccording to this invention, an actuator element having a fixed end and a magnetizable deflection end is releasably held in spring loaded condition at a non-operative position by an electromagnetic operator means. In the preferred form, the actuator element is an elastic beam of magnetically permeable material. The operator means comprises first and second magnetic field producing means for generating separate magnetic fields of the same polarity proximate the magnetizable deflection end of the actuator element and magnetic core means combined with the field producing means to form at least first and second magnetic holding circuits with the deflection end of the actuator element through a common return path. A release means generates flux in the common return path in opposition to the flux from the field producing means.

Preferably the field producing means comprises permanent magnets polarized in the same direction and the core means comprises an E-core structure having inner, outer and center pole pieces ext:ending from a common connection or base of magnetically permeable material.

3~

The permanent magnets are supported by the inner and outer pole pieces. The center pole piece acts as the common return path for the combined flux from the permanent magnets through the magnetizable deflection end of the actuator element. A winding on the center pole piece is energi7able to counteract the flux from the magnets in the center pole piece thereby releasing the actuator element for movement to an actuated position. In one embodiment, the center pole piece extends beyond the permanent magnet surfaces to make contact with the deflection end forming an air gap between the permanent magnets and the magnetizable deflection end of the actuator element. In another embodiment, the center pole piece is recessed from ~he surfaces of the permanent magnets and the actuator element carries an armature piece at its deflection end which is positioned between the permanent magnets in the recess. The winding of the center pole piece preferably extends beyond the end of the center pole piece so as to enclose the armature within the winding.
The end of the center pole piece in ei-ther embodiment may also have a rounded or convex contact surface, preferably spherical and may be covered with a non-magnetic residual material.

In the preferred embodiment, the actuator element is an elastic beam of magnetically permeable material having its fixed end attached to the base member of the core means.
The deflection end of the elastic beam has an end portion capable of being magnetized at or near saturation by the holding flux from the permanent magnet on the outer pole piece. A magnetic focusing plate is provided over the permanent magnet on the outer pole piece for concentrating flux from the permanent magnet into the end portion of the elastic beam. The end portion of the elastic beam is preferably tapered to reduce its mass thereby increasing the velocity of the actuator element and insuring operation at or near saturat:ion.

Preferably the end portion of the elastic beam terminates in a tab sf~ction of reduced width which extends over the magnetic surface of the permanent magnet on the outer pole piece. The elastic beam supports a raised impactor suxface at its deflection end with the tab section extending beyond the impactor surface.

The invention also comprises a hammer mechanism assembly in which the permanent magnets and pole pieces are elongate and have a length coextensive with a plurality of hammer element positions. Individual pole pieces are located at the hammer positions between the first and second pole pieces forming a common flux return path for flux from the first and second permanent magnets to said first and second pole pieces.
Individual resilient magnetic hammer elements are coupled to the magnetic structure in each of the hammer positions.
Each hammer element has a deflection end disposed for magnetization and normal retraction in spring loaded condition by the permanent magnetsn Windings on the individual pole pieces are electrically operable to oppose flux from the permanent magnets in the individual pole pieces to release individual hammer elements. The permanent magnets are preferably strip magnets extending over the surface of the pole pieces over a plurality of print hammer positions. A focusing means comprises a focusing plate of soft iron on the surface of the permanent magnet on the outer pole piece.

In both the single actuator and plural actuator embodiments, means is provided for adjusting the holding force of the operatin~ means. In the preferred form, the adjustment is made by ,altering the amount of flux in the inner magnetic holding circu.it.

L ~ 3 For that purpose the magnetic shunt associated ~71th the inner permanent magnet an~ the inner pole piece is provided.
The shunt is made adjustable for altering the reluctance o~
the shunt circuit. One form of adjustable shunt cornprises a bolt of magnetically permeable material having a threaded connection w~th the base member where the bolt has an end disposed to form a shunt air gap with the deflection end of the beam in the vicinity of the inner permanent magnet. An alternate construction provides for a soft iron pole piece on the inner permanent magnet having a surface forming an air gap with the deflection end of the beam. The shunt element of magnetically permeable material is threadedly connected to the magnetic base member and is disposed to form an air gap with the soft iron pole piece. In a further alternative arrangement, the means for adjusting the reluctance is interior to the inner pole piece. For that purpose, a spacer is provided of magnetic material between the inner permanent magnet and the inner pole piece. A
threaded bolt extends through an opening in the inner pole piece and through the opening in the spacer and is threadedly connected to the inner pole piece so as to be movable to vary the magnetic coupling between the inner permanent magnet and the inner pole piece. In this manner the holding force of the elastic beam can be precisely adjusted to compensate for variations in magnetic strength of the permanent magnets and spring rate variances of the elastic beams. This is particularly advantageous in multiple hammer assemblies where due to tolerance variations the operating characteristics of individual hammers may vary suhstantially. By adjusting the reluctance o-f the inner holding circuil, ~light time corrections can be made without altering the slarting positions of the individual hammers as estab:Lished by the center pole piece which engages with the deElection end of the hammer elements.

-Furthermore, the provision of a focusing plate on the outer magnet assures concentration of flux from the outer permanent magnet into the end of the elastic beam. This assures that each hammer element is operating at or near saturation such that when adjacent hammer elements are released the magnetic holding force on the non-re]eased hammers does not appreciably change.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

Brief Description Of The Drawings Fig. 1 is a perspective drawing showing a multiple print hammer assembly incorporating the various features of the invention.

Fig. 2 is a front view of a portion of the hammer assembly structure of Fig. 1.

Fig. 3 is a side elevation of the hammer assembly of Fig. 1.

Fig. 4 is an enlarged view of a portion of the hammer assembly of Fig. 3.

Fig. 5 is a top view of a second embodiment of a print hammer in accordance with the invention.

Fiy. 6 is a side elevation of the print hammer of Fig. 5.

~N9-80-011 Fig. 7 is a side elevation showing a print hammer actuator with a first embodiment of the adjustable shunt magnetic circuit.

Fig. 8 is a side elevation showing a second embodiment of an adjustable shunt magnetic circuit for a print hammer actuator~

Fig. 9 is a side elevation showing a third embodiment of the adjustable shunt circuit for a print hammer actuator.

Best Modes For Carr~ing Out The Invention As seen in Figs. 1 and 3, an embodiment of a multiple hammer unit assembly incorporating the features of the invention includes a core means comprising base member 10 having outer pole piece 11 inner pole piece 12 and a support post 13.
Base member 10, pole pieces 11 and 12 and support post 13 may all be fashioned from a single block of magnetically permeable material. Alternatively, the base member 10 pole pieces 11 and 12 and post 13 can be separately fabricated from magnetically permeable material and attached together by bonding or some other suitable means for the arrangement shown. Furthermore, post 13 could also be made of a non-ma~netic material. Pole pieces 11 and 12 and post 13 are preferably elongate so as to extend over several print hammer positions. Flexible hammer elements 14 are fixed at one end to surface 15 of post 13 in the manner of elastic cantile~er beams at uniformly spaced positions by suitable means such as clamping plate 16 and screws 17. Surface 15 of post 13 is preferably slanted givin~ hammer elements 14 an outward print or actuated position when in their unflexed conditiorl as illustrated by the broken lines in fi~ure 3.
~n a preEerred embodiment, the flexible ~N9-80-011 ?~

hammer elements 14 are ~abricated as integral fingers of a single plate in which the fingers are foxmed and shaped in a single fabrication operation.

The hammer elements 14 are norma:Lly held in a retracted, spring loaded, non-print position (as shown by the solid lines in figure 3) by magnetic forces produced by two permanent magnets 20 and 21 coup:Led to the faces of poles pieces 11 and 12. The permanent magnets 20 ~nd 21 are elongate strips which cover multiple hammer positions depending on the number of print positions per hammer unit.
More than one magnet strip may be applied to each pole piece each cov~ering one or more hammer positions. Suitable material for the strip magnets 20 and 21 can be one of the high energy prod~lct magnets such as Samarium Cobalt SmCo5 having a thickness of approximately .060 inches. ~ focusing plate 22 of thin, soft iron, e.g. .020 inches or other suitable magnetically permeable material is applied over the outer ma~net 20.

PreferabL~ hammer elements 14 are integral fingers fabricated from a single sheet of magnetically permeable material such as 8620 steel having uniform thickness and extendinq from the fixed end attached to post 13 to the de~lection end which extends above strip permanent magnet 20 and the :Lower edge of strip magnet 21 and 22. ~t their deflection end, hammer elements 14 have a tab portion 26 of reduced ~idth extending from a tapered portion 27. Impactor blades 28 o~ non-magnetic material are attached to tab section 26. The amount of tapering and the dimensions of the tab csection 26 as well as other dimensions of hammer element :L4 can vary depending on the desired spring rate and maglletic permeability of the hammer elements relative to the malgne-ti~ strength o~ the permanent strip magnets 20 and 21.

~ 1 0--Impactor blades 28 can take various forms but preferably are designed for impacting impression forming elements of a type element such as the dot band me~er descrlbed in said co-pending application of ~.D. Thorne. For such application the impactor blades 28 may have a horizontal dimension equal to several character spaces. Alternatively other impactor elements may be used on hammer elements 14 in place of the blades 23 for forming dot impressions directly on a print medium (not shown) with the impactor element attached to the hammer element being shaped accordingly, i.e. as a cylindrical protrusion from the tab sections 26.

Also included in the multiple hammer embodiment of the invention are individual center pole pieces 30 of magnetically permeable material each surrounded by an electric coil 31 wound on a bobbin 32. Coils 31 are connectable for energization to an external power source via connector pins 40. Center pole pieces 30 which are located in line with each hammer element position between p~ole pieces 11 and 12 extend outwardly from base portion lO to form an E-core structure. The center pole pieces 30 terminate in a pole face 33 covered with a cap 34 of non-magnetic residual material. Center pole pieces 30 are made to extend beyond the respective surfaces of focusing plate 22 and inner permanent magnet 21 so that surface 35 on cap 34 makes contact with tab sections 26 of the hammer elements 14 when in their retracted position so as to maintain an air gap 36 between the focusing plate 22 and tab 26 and also between permanent magnet 21 and hammer element 1~. Surface 35 of residual cap 34 is rounded or convex preferably with a spherical contour. The convex or spherical contour is primarily to insure contact over a large radius and to prevent impact of hammer elements 14 on center pole piece edges which would concentrate wear and may cause settle out problems due to the han~er elements 14 striking center pole pieces 30 at locations other than the center of percussion. ~ threaded connection 37 attaches center pole piece 30 to base member lO and allows rotation of center pole pieces 30 in a well known manner to adjust the air gaps 36 thereby readily making adjustments in the flight times of the individual hammer elements 14 to compensate for tolerance variations in spring rate characteristics of the hammer elements 14.

In accordance with the invention the permanent magnets 20 and 21 are polarized in the same direction and are supported and magnetically coupled to the E-core structure made up of the base member lO, outer pole piece 11l innex pole piece 12 and the individual center pole pieces 30. As shown more clearly in Figure 4, the magnetic surface structure of the invention produces dual closed magnet holding circuits for holding each hammer element 14 in spring loaded condition.
In the outer magnetic holding circuit magnetic flux, as shown by broken line 38, from permanent magnet 20 passes through outer pole piece 11 through base member 10 and returns through center pole piece 30 across cap 34 into the extremity of tab portion 26 across gap 36 to focusing plate 22. In the second or inner magnetic holding circuit magnetic flux, indicated by broken line 39, from permanent magnet 21 passes throu~h inner pole piece 12 and center pole piece 30 into the inner part of tab portion 26 of the hammer element 14 and across gap 26~ The same magnetic flux paths exist for each of the hammer elements. Thus center pole pieces 3~) provide a common return path for holding flux from both permanent strip magnets 20 and 21. The strip permanent magnets 20 and 21 can be made relatively thin thereby producing a compact physical and magnetic structure~ Additionally with the added benefit from focus plate 22, a holding force on the hammer elements 14 ak the end hammer positions is apprec.iably improved compared to a magnetic structure without a focusing plate. Thus the wasted space and material realized with use of dummy hammer positions is avoided., Because flux from both magnets 20 and 21 passes in the same direction through a common return path provided by the center pole pieces the selective release of the individual hammer elements is expeditiously performed simply by energizing the desired coils 31 with current applied through connector pins 40 in the direction which produces a counter flux sufficient for reducing the magnetic holding force of both holding circuits on tab portions 26. The common flux return path provides a convenient site for generating the release flux without the need for or concern about reverse polarizing one or both permanent magnets, which are preferably made from very high coercivity materials, and without the need for shunting counter flu~ to prevent weakening or reverse polarization of the permanent maynets.

In the hammer mechanism assembly of figures 5 and 6, the resilienk hammer elements 14 may be formed of nonmagnetic material. ~ magnetic armature 41 is attached to the deflection end of elements 14 directly behind the impact blade 28. The deflection end of hammer elements 14 has a section 42 which is tapered to reduce the thickness of the deflection end. Tapering significantly reduces the e~fective mass of element 14 and compensates somewhat for the increased phys.ical mass of armature 42. A suitable non-magnetic material or the hammer elements can be ; titanium.

In the embodiment of Figures 5 and 6, flux concentration is provided by focusing plate 43 which overlays both permanent magnets 20 and 21 as well as post 13 which is preferably non-magnetic where it is attached with hammer elements 14 by plate 44 and screws 45. The slanted surface 46 on focusing plate 43 cants the hammer elements 14 outwardly when in their unflexed condition. Focusing plate 43 has a rectangular opening 47 aligned with center pole pieces 30.
Armatures 41 on the hammer elements 14 extend through the openings 47 to make physical contact with the rounded pole face 48 of center pole pieces 30 which in this case are recessed below the upper surfaces of permanent magnets 20 and 21 so that armatures 41 in their retracted spring loaded as well as in the released position align with the permanent magnets 20 and 21. In retracted condition, armatures 41 make contact with pole face 48 of center pole piece 30 but maintains an air gap 4g between the deflection end of hammer elemen-ts 14 and focusing plate 43. This low mass structure allows for quick release when release coil 31 on center pole piece 30 is energized to produce counter flux opposing flux from both permanent magnets 20 and 21 in the common return path. The magnetic mass of armatures 41 is as small as possible, however a low reluctance flux path is provided from permanent magnets 20 and 21 through flux plate 43 and across opening 47 to readlly magneti~e armatures 41 at or near the saturation level while providing sufficient stored energy in beam 14 for proper actuating characteristics.

Figs. 7~9 show other arrangements for obtaining flight time adjustments. In some cases, adjustment at the air gap between the harnmer elements and the permanent magnets may not be desir~ble since this alter, however slightlv, the 1e~ure force and flight path length of the spring loaded hanuner elements.

As seen in the schematized structure of Figure 7, center pole piece 30 is fixed and its polP face 33 with residual layer 49 extend a fixed distance beyond the surfaces of focusing plate 22 on the outer pole piece 11 and inner permanent magnet 21. In this arrangement a bolt 50 o~
magnetically permeable material having a threaded connection 52 to base member 10 forms a shunt circuit path with inner permanent magnet 21 and inner pole piece 12 for diverting holding magnetic flux from permanent magnet 21 to center pole piece 30. The reluctance of the shunt circuit path is variable by adjustment of the bolt 50 to modify an air gap 53 between the end of magnetic bolt 50 and the magnetic hammer element. The amount of magnetic flux diverted from the inner permanent magnet 21 to bolt 50 is dependent on the dimension of the shunt air gap 53. This in turn adjusts the magnitude of the holding force from inner permanent magnet ; 21 of the inner holding circuit comprising inner permanent magnet 21, inner pole piece 12, center pole piece 30 and the deflection end of magnetic hammer element 14.

As seen in Figure 8, the shunt circuit includes a soft iron plate 54 superimposed on the inner permanent magnet 21 : whereby a fixed air gap is maintained between the inner holding circuit and the hammer element. Plate 54 overhangs and is aligned with the end of bolt 50. The threaded connection 52 allows bolt 50 to be adjustable for modifying the shunt air gap 55 between the bolt 50 and plate 54. This arrangement also allows adjustment of the reluctance of the inner shunt circuit for diverting magnetic flux from the inner holding circuit thereby reducing the total holding force on the individual hammer elements 14.

As seen in Figure 9, the holding force adjustment is obtained by a shunt circuit which is internal to the inner pole piece 120 A magnetic bolt 50 within threaded opening 57 through magnetic pole piece 12 extends to the end of the pole piece. A magnetically permeable plate 56 is positioned on top of a non-magnetic specer 58 on the pole piece 12 below permanent magnet 21. Clearance hole 59 through spacer 58 is aligned with bolt 50. Rotation of bolt 50 in threaded opening 57 modifies and adjusts the reluctance of the inner pole piece 12 to thereby divert more or less flux from the center pole piece to modify the holding force on hammer element 14.

Claims (36)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A hammer device comprising a flexible hammer element having a fixed end and a magnetizable deflection end, said hammer element having a bias toward an impact position when deflected to a non-impact position, electromagnetic operating means for retracting from said impact position and releasably holding said deflection end of said hammer element against said bias at a deflected non-impact position whereby impact energy is stored in said hammer element, said electromagnetic operating means including magnetic circuit means comprising a first permanent magnet adjacent said magnetizable deflection end of said hammer element, said first permanent magnet producing a first magnetic field in the vicinity of said deflection end of said hammer element, a second permanent magnet adjacent said deflection end of said hammer element, said second permanent magnet producing a second magnetic field of the same polarity as said first magnetic field in the vicinity of said deflection end of said hammer element,
1. Claim 1 continued core means of magnetically permeable material coupled with said first and second permanent magnets, said core means and said first and second permanent magnets defining first and second magnetic holding circuit flux paths with a pair of air gaps adjacent.
   said magnetizable deflection end whereby said deflection end of said hammer element extends over said pair of air gaps, said core means including a common flux return path member between said first and second permanent magnets and coacting therewith to form said pair of air gaps, and release means operable for generating flux in said return path member opposing flux from said first and second permanent magnets.
   
   2. A hammer device in accordance with claim 1 in which said first and second permanent magnets have magnetic surfaces of the same polarity proximate said magnetizable deflection end of said hammer element,
2. Claim 2 continued said common flux return path is a pole portion of said core means extending between said permanent magnets, and said release means includes an electrically energizable winding on said pole portion.
3. 3. A hammer device in accordance with claim 2 in which said pole portion extends beyond said magnetic surfaces of said permanent magnets for engaging said deflection end of said hammer element at said non-impact position whereby an air gap is maintained between said magnetic surfaces of said first and second permanent magnets and said deflection end of said hammer element.
4. 4. A hammer device in accordance with claim 3 in which said pole portion has adjustment means whereby said pole portion is movable relative to said magnetic surfaces of said permanent magnets for adjusting said air gap between said deflection end of said hammer element and said magnetic surfaces of said permanent magnets.
5. 5. A hammer device in accordance with claim 4 in which said core means includes a magnetic base member and said pole portion is a pole piece having a threaded connection with said base member, said pole piece is rotatable in said threaded connection for adjusting said air gap between said deflection end of said hammer element and said magnetic surfaces.
6. 6. A hammer device in accordance with claim 5 in which said magnetic surfaces of said permanent magnets are substantially coplanar and, said pole piece has residual material on the end thereof for engaging said deflection end of said hammer element, said pole piece being rotatable whereby said threaded connection provides adjustment of the said air gap of said deflection end with said coplanar magnetic surfaces of said permanent magnets.
   
   7. A hammer device in accordance with claim 2 which further includes a base member supporting said hammer element at said fixed end and said core means adjacent said deflection end of said hammer element,
7. Claim 7 continued and said hammer element is an elastic beam having said fixed end attached to said base member and said deflection end proximate said magnetic surfaces of said first and second permanent magnets and extending over said pair of air gaps.
8. 8. A hammer device in accordance with claim 7 in which said core means comprises an E-core structure carried by said base member at said deflection end of said elastic beam, said E-core structure having outer and inner pole pieces coupled to and supporting said first and second permanent magnets respectively and a center pole piece proximate said deflection end of said beam forming said common flux return path member and supporting said electrically energizable winding for generating said opposing flux.
9. 9. A hammer device in accordance with claim 8 in which said base member is made of magnetically permeable material, and said elastic beam is made of magnetically permeable material having its fixed end attached to said base member.
10. 10. A hammer device in accordance with claim 8 in which said deflection end of said elastic beam has an end portion extending over said first permanent magnet, said end portion being capable of being magnetized at least near saturation by flux from said permanent magnet on said outer pole piece.
11. 11. A hammer device in accordance with claim 10 in which said magnetic circuit means further includes a magnetic focusing plate for concentrating flux from said first permanent magnet into said end portion of said elastic beam.
12. 12. A hammer device in accordance with claim 10 in which said end portion of said elastic beam is tapered so as to be capable of being magnetized at least near saturation.
13. 13. A hammer device in accordance with claim 12 in which said tapered end portion of said elastic beam has its thickness tapered.
14. 14. A hammer device in accordance with claim 12 in which said tapered end portion of said elastic beam has its width tapered.
15. 15. a hammer device in accordance with claim 14 in which said tapered end portion has a reduced width tab section extending from said tapered width section, said tab section extending over and proximate said magnetic surface of said first permanent magnet of said outer pole piece, said tab section being magnetizable at or near saturation by said permanent magnet of said outer pole piece.
16. 16. A hammer device in accordance with claim 15 in which said hammer element supports a raised impactor surface at its deflection end and said tab section extends beyond said impactor surface.
17. 17. A hammer device in accordance with claim 16 in which said impactor surface is a longitudinal bar attached to said tapered width section of said elastic beam, said bar being positioned for alignment with said center pole piece of said E-core structure.
    
    18. A hammer device in accordance with claim 8 in which
18. Claim 18 continued said center pole piece extends beyond said magnetic surfaces of said first and second permanent magnets into engagement with said deflection end of said hammer element at said non-impact position for maintaining an air gap between said magnetic surfaces and said deflection end of said hammer element.
19. 19. A hammer device in accordance with claim 18 in which said center pole piece of said E-core structure is adjustable relative to said inner and outer pole pieces for modifying said air gap between said deflection end of said hammer element and said magnetic surfaces of said first and second permanent magnets when held in said non-impact position.
    
    20. A hammer device in accordance with claim 8 in which said center pole piece of said E-core structure is recessed below said magnetic surfaces of said permanent magnets, and said deflection end of said beam has an armature element of magnetically permeable material disposed between said permanent magnets for engaging the end of said recessed center pole position at said non-impact position,
20. Claim 20 continued said armature element being magnetizable at least near saturation by flux from said permanent magnets.
21. 21. A hammer device in accordance with claim 20 in which said electrically energizing winding on said center pole piece has an extension portion which extends beyond the recessed end thereof and said armature element is located within said extension portion of said winding when in engagement with said center pole piece.
22. 22. A hammer device in accordance with claim 9 which further comprises means for adjusting the magnetic holding force of one of said first and second permanent magnets relative to the other on said deflection end of said beam.
23. 23. A hammer device in accordance with claim 22 in which said means for adjusting said magnetic holding force comprises means for altering the amount of flux in the inner magnetic holding circuit comprised of said inner permanent magnet, said deflection end of said beam and said center and inner pole pieces of said E-core structure.
24. 24. A hammer device in accordance with claim 23 in which said means for altering the amount of flux in said inner magnetic holding circuit comprises an adjustable magnetic shunt means associated with said inner permanent magnet and inner pole piece so as to form a shunt circuit therewith.
25. 25. A hammer device in accordance with claim 24 in which said adjustable shunt means comprises a bolt of magnetically permeable material having a threaded connection with said base member, said bolt having an end disposed to form a shunt air gap with said deflection end of said beam in the vicinity of said inner permanent magnet, and said shunt air gap is adjustable by turning of said bolt in said threaded connection.
26. 26. A hammer device in accordance with claim 24 in which said shunt circuit further comprises a soft iron pole piece on said inner permanent magnet having a surface forming an air gap with said deflection end of said beam, and a shunt element of magnetically permeable material threadedly connected to said magnetic base member, said shunt element being disposed to form an air gap with said soft iron pole piece.
27. 27. A hammer device in accordance with claim 26 in which said shunt circuit includes means for adjusting the reluctance of said inner pole piece of said E-core structure.
28. 28. A hammer device in accordance with claim 27 in which said means for adjusting the reluctance of said inner pole piece comprises spacer means of non-magnetic material in said inner magnetic holding circuit between coupled surfaces of said inner pole piece of said E-core structure and said inner permanent magnet, said spacer having an aperture therethrough aligned with an aperture through said inner pole piece, and a magnetic bolt member coupled with said inner pole piece and movable axially within said aperture in said spacer relative to said inner permanent magnet for adjusting the reluctance between said inner permanent magnet and said inner pole piece.
    
    29. A hammer mechanism assembly comprising an elongated magnetic circuit structure including first and second permanent magnets of the same polarity extending in parallel along the length of said magnetic circuit structure, core means of magnetically permeable material having first and second pole pieces coextensive with said permanent magnets, the length of said magnetic structure being coextensive with a plurality of hammer element positions, said core means further including individual pole pieces at each hammer position between said first and second pole pieces and forming a pair of air gaps at each hammer position with said first and second permanent magnets, said pole pieces forming a common flux return path at each hammer position for flux from said first and second permanent magnets to said first and second pole pieces, individual resilient magnetic hammer elements coupled to said magnetic circuit structure in each of said hammer positions, each of said hammer elements having a fixed end remote from and a deflection end in the vicinity of said first and second permanent magnets so as to extend over said pair of air gaps so as to be disposed for magnetization and retraction of said hammer elements in spring loaded condition to a non-impact position by flux from said first and second permanent magnets through said individual and said first and second pole pieces,
29. Claim 29 continued and windings on said individual pole pieces electrically operable to counteract flux from said first and second permanent magnets in said individual pole pieces for the release of said individual hammer elements for movement by a bias force from said non-impact position.
30. 30. A hammer assembly in accordance with claim 29 in which said core means has an E-core structure in which said first and second pole pieces are inner and outer pole pieces respectively coupled with said first and second permanent magnets respectively and said individual pole pieces are center pole pieces forming said common flux return path, and said individual center pole pieces extend beyond said first and second permanent magnets and have a pole face in said engagement with said deflection end of said hammer elements so as to maintain an air gap between said deflection end and said first and second permanent magnets at said non-impact position.
31. 31. A hammer assembly in accordance with claim 30 in which said center pole pieces have means for individually adjusting said center poles relative to said inner and outer pole pieces for varying said air gap between said deflection end of said hammer elements and said first and second permanent magnets.
32. 32. A hammer assembly in accordance with claim 30 in which said permanent magnets are strip magnets on said inner and outer pole pieces extending over a plurality of said hammer element positions.
33. 33. A hammer assembly in accordance with claim 32 which further includes focusing means for concentrating flux from strip magnet on said outer pole piece across an air gap into an end section of said deflection end of said hammer elements.
34. 34. A hammer assembly in accordance with claim 33 in which said focusing means comprises a focusing plate of soft iron on the surface of said permanent magnet on said outer pole piece.
35. 35. A hammer assembly in accordance with claim 34 in which said end section of said hammer elements is magnetizable at least near saturation by flux from said strip magnet.
    
    36. An actuator mechanism comprising an actuator element having a fixed end and a magnetizable deflection end, said actuator element having a bias toward an operated position,
36. Claim 36 continued operating means for retracting and releasably holding said actuator element against said bias at a deflected non operated position whereby impact energy is stored in said actuator element, said operating means including a magnetic circuit structure comprising first and second magnetic field producing means for generating separate magnetic fields of the same polarity proximate said magnetizable deflection end of said actuator element, magnetic core means associated with said first and second field producing means to form at least first and second flux paths with said deflection end of said actuator element through a common flux return path member between said field producing means, said first and second flux paths including a pair of air gaps between said first and second field producing means and said return path member, and release means operable for generating flux in said common return path member in opposition to flux from said field producing means.