DocketNumber： Patent Appeal No. 7809
Citation Numbers： 386 F.2d 909
Judges： Almond, Smith
Filed Date： 11/24/1967
Status： Precedential
Modified Date： 11/26/2022
This appeal is from the decision of the Board of Appeals affirming the rejection on prior art of claims 9 and 10 of appellants’ application
The invention relates to “time of flight” mass spectrometers of the right angle entry type wherein gaseous molecules, which are either received in ionized state or ionized in the spectrometer, are accelerated electrically in a direction perpendicular to their original direction and the accelerated ions are received and measured by means which distinguish them according to their masses. More specifically, the ions are exposed to a pulsed accelerating field so as to be directed toward a collector forming part of a detecting means. The time of arrival of the ions accelerated by each pulse is determined by their respective masses since the lighter ions are accelerated more than those of greater mass. The detecting means operates in syn-chronism with the accelerating pulses to provide an indication of the relative number of ions of each mass in the beam.
As noted by appellants, the right angle entry feature minimizes the background or stray ions in the output of the spectrometer so that the measurement is a more true representation of the quantity of source particles which it is desired to analyze. Thus stray or background ions are accelerated substantially in the direction of the accelerating field while the source particles are accelerated in a direction which is the resultant of the initial entry velocity and the velocity imposed by the accelerating field and the collector is located in the latter direction.
Appellants point out that the right angle direction of the accelerating field causes less bending from the original direction of the heavier ions than the lighter ones so that the ions of different masses in the beam directed toward the collector tend to diverge. They state that electric or magnetic fields may be provided to act on the accelerated beam in a direction transverse to the beam to provide a converging force which tends to overcome the divergence and results in a greater proportion of the source particles falling on the collector. In a first embodiment, appellants employ a constant electric field for converging purposes, stating that the heavier particles are deflected more than the lighter particles because such heavier particles are slower and thus are under the influence of the field for a longer time.
In a second embodiment, appellants describe analysis of ionized particles col
Another embodiment differs from that just described in that the structure for producing the varying electric deflecting field is replaced by means producing a constant strength magnetic field in a direction transverse to the accelerated direction of the ions to produce a similar converging effect thereon.
Claims 9 and 10, respectively, are directed to the aforementioned latter two embodiments and read:
9. An acceleration system for charged particles comprising,
particle accelerating means,
means for conducting charged particles traveling in a first direction towards said particle accelerating means,
substantially all of said charged particles traveling in said first direction having the same speed,
said particle accelerating means having an accelerating field direction other than said first direction for accelerating said charged particles in a resultant direction,
particle receiving means positioned in a path of said resultant direction a predetermined distance from said accelerating means for receiving charged particles traveling only in said resultant direction,
control means situated along the resultant direction for imparting a force to the particles as they pass a distance through said control means to reduce particle divergency and influence said particles to travel a uniform common direction thereby establishing better beam definition,
said control means comprising means for applying an increasing electric field in-a direction having components transverse to said resultant direction to apply a correction force to said particles to minimize the divergency of said particles.
10. An acceleration system for charged particles comprising,
particle accelerating means,
means for conducting charged particles traveling in a first direction towards said particle accelerating means,
said particle accelerating means having an accelerating field direction other than said first direction for accelerating said charged particles in a resultant direction,
particle receiving means positioned in a path of said resultant direction a predetermined distance from said accelerating means for receiving charged particles traveling only in said resultant direction,
control means situated along the resultant direction for imparting a force to the particles as they pass a distance through said control means to reduce particle divergency and influence said particles to travel a uniform common direction thereby establishing better beam definition,
said control means comprises means for exerting a constant magnetic field which is in a direction to change the course of the charged particles to cause said charged particles to converge.
*912 The references relied on below are:
Benson et al. 2,938,116 May 24,1960 (Benson)
Schroeder 2,696,561 December 7, 1954
Van Nostrand’s Scientific Encyclopedia published by D. Van Nostrand Co., Inc., 3rd Ed., 1958, pages 1030-1033.
Benson discloses a time of flight mass spectrometer utilizing a right angle entry system. The spectrometer utilizes a deflecting means shown in figure 7 of the patent for applying a converging force on the ions traveling toward the collector. The system comprises two focusing plates across which a constant electrical voltage is applied.
Schroeder discloses certain mass spectrometers wherein time of flight is utilized to distinguish ions of different mass and others which distinguish between different ions by the action of deflection means which focus them at different locations or at the same locations at different times. It discloses the use of electric deflecting fields provided by either a steady uniform voltage or by voltage pulses, magnetic fields which are either constant or variable, and combinations of electric and magnetic fields, including a variable electric field used with a constant magnetic field.
Van Nostrand describes mass spectrometers generally and includes a description of an instrument known as the Aston mass spectrometer. In that device, a magnetic field is used to focus an ion beam to produce charge lines on a photographic plate which receives the ion beam.
The issue here is obviousness under 35 U.S.C. 103. Aside from that issue, there is no significant legal question in dispute.
Claim 9 stands rejected on Benson taken in view of Schroeder on the ground that the latter reference would make it obvious to employ a variable electric deflection field in place of the constant field employed in Benson. Claim 10 was rejected as unpatentable over Benson on the ground that it would be obvious to substitute a constant magnetic field for the constant electric field as the ion stream converging means in Benson. The examiner and the board both regarded magnetic and electric fields as known equivalents for deflecting charged particles, referring, respectively, to Van No-strand and Schroeder as supporting that position.
Appellants urge that the board erred in the rejection of claim 9 because the deflecting plates of Benson et al. are for focusing an ion beam while the deflecting plates in Schroeder are for separating an ion beam and it is not believed that one skilled in the art would be led to two patents of opposing objects to solve a problem. They also urge that Schroeder’s disclosure of a great many embodiments would make it difficult for one skilled in the art to select a particular portion of a particular embodiment to combine with Benson. They further contend that “[pjrevious systems have used constant voltage fields for constant energy source particles while this invention uses a variable voltage field for convergence of constant velocity source particles.”
We do not find any significant distinction in this last contention of appellants. While claim 9 is limited to an arrangement in which substantially all the charged particles are traveling at the same speed when received in the system, the subsequent action of the accelerating field on the particles causes those of different masses to travel at different velocities and it is those very differences in velocity that are utilized for segregating the particles by mass according to their
In support of the rejection, the examiner pointed out that Schroeder shows that electrostatic fields impressed on ions in a mass spectrometer to control their deflection may be constant or variable and regarded it obvious that the same is true for control means of the type disclosed by Benson. Nothing is seen in appellants’ arguments to controvert that position successfully. It seems apparent that a person of ordinary skill in the art with Schroeder before him would be aware of what differences in deflection effects would be produced by a constant electric field on the one hand and a variable or increasing field on the other and would be qualified to choose between such fields in accordance with the effect desired.
Moreover, the examiner further specifically suggested that it would be obvious “to employ the variable electrostatic field control means shown in Figs. 19 and 21 of Schroeder in place of the constant electrostatic field control means 135 (Fig. 7) of Benson et al.” The ■forms of the Schroeder device shown in those two figures apply short voltage pulses to the deflecting plates in syn-chronism with pulses accelerating the ions initially. Obviously referring to that feature of Schroeder, the solicitor urges:
Further, appellants’ claims do not specify any particular manner of applying increasing voltage to the deflection means, and no reason has been advanced why a pulsating voltage synchronized with the acceleration pulses as taught by Schroeder would not be suitable.
Observing that appellants have not responded to that argument of the solicitor and that the terminology of claim 9 is indeed as broad as urged, we conclude that the rejection of the claim on the basis of the substitution of a pulsating deflecting voltage for energizing the deflecting plates of Benson is free of reversible error. Therefore, the decision as to claim 9 is affirmed.
Claim 10, being drawn to a different aspect of the invention, raises a somewhat different question. The examiner stated that “it is well known that magnetic or electrostatic fields are fully equivalent for the purpose of particle deflection,” and referred to the Aston mass spectrometer described in Van Nostrand as involving the use of a magnetic field to focus an ion beam. The board referred to Schroeder as evidence that electric and magnetic fields can be used interchangeably to deflect a beam of charged particles.
We think that each of Van Nostrand and Schroeder would suggest to a person skilled in the art that a constant magnetic field be provided in place of the constant electric field disclosed by Benson for focusing the ions in the beam. Van No-strand clearly discloses that a magnetic field may be used to focus a beam of ions. While the electric and magnetic fields of Schroeder are used in different systems than that of Benson, the former patent does reveal that the two types of fields can be used to produce similar effects on charged particles.
Appellants assert that Benson and Schroeder show that the involved art is a crowded one and urged that “smaller steps forward are deemed patentable” in such circumstances. However, the criterion on which patentability must be resolved here is obviousness under 35 U.S. C. § 103 and, on that basis, we are convinced from the record and arguments that claims 9 and 10 are not patentable.
It is noted that appellants have not discussed the merits of the Van Nostrand reference in their brief. Instead, they refer to a reference, cited for the first time in the Examiner’s Answer, that “allegedly shows a magnetic field for the focusing of ions.” They assert that they “have not had sufficient time to examine the reference” and contend that prosecution should be reopened if the reference
The decision of the board is affirmed. Affirmed.
. Serial No. 229,519, filed October 5, 1962.