OSCILLATING BAR SUSPENSION SYSTEM

Abstract: In the oscillating bar suspension system described in the specification, a spring member (22) has seven legs (23-29) with alternate legs affixed at their outer ends to a support member (20) and to projecting extensions of an oscillating bar (10) to distribute the stress induced in the spring by oscillation of the bar over six stress points (30). The oscillating bar carries an ink jet head and is driven by a transducer which produces a desired displacement of the bar at desired frequency to produce a selected pattern on a record sheet during operation of the ink jet head.

Description: Description Oscillating Bar Suspension System Technical Field This invention relates to oscillating bar suspen- sion systems and, more particularly, to a new and improved suspension system for an oscillating bar having increased durability. Background Art In United States Patent No. 4,322,063, a suspen- sion for an oscillating bar is described wherein two trifurcated springs are disposed at opposite ends of a suspended bar. Each of the trifurcated springs has two outer legs with ends affixed to a support struc¬ ture and a central leg with its end affixed to the oscillating bar. With this arrangement, the oscillat¬ ing bar is supported for longitudinal motion while being restrained against lateral motion or motion in an angular direction. Oscillating bars supported by such suspension systems may be driven in a continuous manner by a solenoid, for example, producing substantial displace¬ ment of the oscillating bar at a relatively high fre¬ quency in a continuous manner. Such operation gener¬ ates substantial stresses in the trifurcated spring, especially at the junctions between the legs of the spring, tending to cause failure of the springs during operation. Strengthening of the trifurcated spring members by increased thickness or width, however, changes the spring constant, and thus varies the char- acteristics of the suspension system in an undesirable manner. Disclosure of Invention Accordingly, it is an object of the present in¬ vention to provide an improved oscillating bar suspen¬ sion system which overcomes the above-mentioned disad- vantages of the prior art. Another object of the invention is to provide an improved oscillating bar suspension system having greater durability and prolonged life. These and other objects of the invention are attained by providing an oscillating bar suspension system having support springs with at least four legs affixed alternately to the oscillating bar and to the support structure. In this way, the stress generated at the stress points between the legs affixed to the support structure and the legs affixed to the oscil¬ lating bar is reduced, prolonging the life of the sup¬ port spring. Further objects and advantages of the invention will be apparent from a reading of the following de- sc iption in conjunction with the accompanying draw¬ ings, in which: Brief Description of Drawings Fig. 1 is a fragmentary plan view illustrating one end portion of a representative oscillating bar suspension system arranged in accordance with the invention; Fig. 2 is a cross-sectional view illustrating the end portion of the suspension system shown in Fig. 1; and Fig. 3 is a side view showing the displacement of the oscillating bar in the oscillating bar suspension system of Figs. 1 and 2. Best Mode for Carrying Out the Invention In the representative embodiment of the invention illustrated in the drawings, an oscillating bar 10 carries an ink jet head 11 for reciprocating motion in the direction of the arrow 12. In this way, the ink jet head 11 may be oscillated with a selected dis¬ placement and frequency so that ink drops projected from the head toward an adjacent record sheet (not 5 shown) which is moved in a direction transverse to the direction of oscillation of the head 11 will produce a desired pattern on the sheet. To produce oscillation of the bar 10 at the de¬ sired displacement and frequency, a transducer 13 10 which may, for example, be an electrical solenoid, is connected by a drive shaft 14 to a projecting end segment 15 of the bar 10. In the illustrated embodi¬ ment, the oscillating bar 10 has two further project¬ ing end segments 16 and 17 which, together with the 15 end segment 15, are disposed in recesses 18 formed between adjacent support members 19 in a fixed support structure 20 for the suspension system. The support structure 20 is affixed to a mounting plate 21 which has a similar support structure (not shown) for the 20 opposite end of the oscillating bar 10. In order to suspend the bar 10 from the support structure 20 for oscillating motion in the direction of the arrow 12 without causing undue stress leading to failure of the suspension system, a suspension 25 spring having at least four legs is provided so as to assure that the stress at the junctions between the legs is below a level which could cause fatigue, cracking, and similar deterioration of the spring material. In the illustrated embodiment, a suspension 30 spring 22 has seven legs 23-29, but, depending on the characteristics of the system and the total stress applied to the spring, the spring may have as many legs as is necessary to distribute the total stress applied to the spring sufficiently to avoid deteriora- 35. tion. As best seen in Fig. 2, the spring 22 is ar¬ ranged with four legs 23, 25, 27 and 29 affixed at their ends by clamps to the support member 19 of the support structure 20 and three legs 24, 26 and 28 affixed at their ends by clamps to the extensions 16, 15 and 17, respectively, of. the oscillating bar 10. Thus, in this embodiment, six stress points 30 are provided between the adjacent legs of the suspension spring. A similar spring (not shown) is provided for the corresponding support structure at the other end of the mounting plate 21 to support the opposite end of the oscillating bar. When the drive element 13 oscillates the bar 10 with a displacement "d" as illustrated in Fig. 3, the total stress applied to the spring is dependent upon the displacement "d" and the stiffness of the spring, which provides the restoring force. In the illus¬ trated embodiment, this stress is distributed uni- formly among the six stress points 30 between the legs 23, 25, 27 and 29 of the spring member which are af¬ fixed to the support members 19 and the legs 24, 26 and 28 which are affixed to the extensions 15, 16 and 17 of the oscillating bar. Thus, in comparison with . the trifurcated spring suspension system shown in Patent No. 4,322,063, for example, which has only two stress points, the stress at each stress point in the illustrated embodiment is reduced by a factor of ap¬ proximately three. Moreover, the stress reduction at each stress point is accomplished without changing the characteristics of the suspension system. With this arrangement, suspension springs for bar suspension systems can be provided which have sufficient durabil¬ ity to assure indefinite life for any type of bar suspension system, regardless of the operating requirements of the system. Although the invention has been described herein with reference to a specific embodiment, many modifi- ' cations and variations therein will readily occur to those skilled in the art. Accordingly, all such vari¬ ations and modifications are included within the in¬ tended scope of the invention as defined by the fol¬ lowing claims.

Claims: Claims 1. An oscillating bar suspension system comprising support means providing a plurality of spaced support elements, oscillating bar means adapted to be supported at a plurality of spaced support points, and support spring means comprising a spring member having at least four spaced leg portions projecting away from a common segment with alternate leg portions affixed to the sup- port elements of the support means and to the support points of the oscillating bar means, respectively, providing at least three stress points at the intersections of adjacent leg por¬ tions of the spring member. 2. A suspension system according to Claim 1 wherein the spring member includes seven leg portions. 3. A suspension system according to Claim 2 wherein four of the leg portions are affixed to the sup¬ port means and three of the leg portions are affixed to the oscillating bar means. 4. A suspension system according to Claim 1 wherein the support means is formed with recesses between the spaced support element, and the oscillating bar means is formed with extensions positioned within the recesses of the support means. 5. A suspension system according to Claim 4 includ¬ ing drive means connected to one of the exten¬ sions for driving the oscillating bar means.

Inventors: FISCHBECK KENNETH H, PILLSBURY TIMOTHY A, FISCHBECK, KENNETH, H., PILLSBURY, TIMOTHY, A.
Applicants: SPECTRA INC, SPECTRA, INC.
Application year: 1988
Main classification: F16F1
IPC codes: B23Q1, B41J2, B41J25, F16F1, F16F15, H04N1