<PAGE>   1
                                                                 Exhibit 10.3.1

                                 FIFTH AMENDMENT
                                       TO
                              ROBBINS & MYERS, INC.
                                  PENSION PLAN

                (as Amended and Restated Effective as of 10/1/89)

         WHEREAS, Robbins & Myers, Inc. (the "Company") maintains Robbins &
Myers, Inc. Pension Plan (the "Plan"); and

         WHEREAS, amendment of the Plan is now deemed desirable;

         NOW, THEREFORE, the Corporate Benefits Committee, acting pursuant to
the authority granted to it by Section 11.1 of the Plan, hereby amends the Plan,
effective October 1, 1994 by substituting the following for subparagraph
6.7(a)(2):

         (2)      LUMP SUM OPTION. A lump sum option is also available under the
                  Plan. The lump sum Actuarial Equivalent value shall be
                  determined on the basis of the benefit that the Member would
                  have been entitled to on the first day of the month following
                  the later of his Normal Retirement Age or the date on which
                  his Vesting Service terminates. Notwithstanding the foregoing,
                  effective for Vesting Service accrued on or after October 1,
                  1994, the value of the supplemental benefit ($3.50 times years
                  of Vesting Service) will not be taken into account when
                  calculating the amount of the Member's distribution under the
                  lump sum option.

                  A Member's election of the lump sum option shall include a
                  waiver of an immediately payable Qualified Joint and Survivor
                  Annuity under section 6.6, together with spousal consent if
                  the Member is married. Such waiver shall not be necessary if
                  the lump sum payment is made pursuant to the provisions of
                  section 6.8.

                  Subject to the waiver described above, the lump sum option
                  described in this paragraph (2) shall be available effective
                  as of October 1, 1989 to all Members other than those who are
                  in pay status, including retirees and terminated vested
                  Members.


<PAGE>   2



         IN WITNESS WHEREOF, the undersigned, a duly appointed member of the
Corporate Benefits Committee, has caused this Fifth Amendment to be executed on
its behalf, this 24th day of September, 1994.

                                       By /s/ 
                                         ------------------------------
                                          A Member of the Corporate
                                          Benefits Committee

                                       -2-


<PAGE>   3



                                 SIXTH AMENDMENT
                                       TO
                              ROBBINS & MYERS, INC.
                                  PENSION PLAN

                (as Amended and Restated Effective as of 10/1/89)

         WHEREAS, Robbins & Myers, Inc. (the "Company") maintains Robbins &
Myers, Inc. Pension Plan (the "Plan"); and

         WHEREAS, amendment of the Plan is now deemed desirable;

         NOW, THEREFORE, the Corporate Benefits Committee, acting pursuant to
the authority granted to it by Section 11.1 of the Plan, hereby amends the Plan,
effective October 1, 1994:

         (1)      By substituting the following for paragraph 2.1(b):

         (b)      "ACTUARIAL EQUIVALENT" means a benefit having the same
                  value as the benefit which it replaces. Except as otherwise
                  provided elsewhere in the Plan, such benefit shall be computed
                  based on such tables as are attached as an exhibit to the
                  Plan, and otherwise computed on the bases of the 1971 Group
                  Annuity Mortality Table, weighted 80 percent male and 20
                  percent female, and on a 7 percent interest assumption.

                  Notwithstanding the above, for purposes of determining single
                  sum cash settlements, the interest rate used shall be the
                  immediate and deferred rate which would be used (as of the
                  first day of the Plan Year in which the distribution occurs)
                  by the Pension Benefit Guaranty Corporation ("PBGC") for
                  purposes of determining the present value of a lump sum
                  distribution upon the termination of a defined benefits plan;
                  provided, however, that if, using that rate, a lump sum
                  benefit is determined to be at least $25,000, the benefit will
                  be recalculated using an interest rate of 120 percent of the
                  PBGC rate described above.

         (2)      By substituting the following for subparagraph
6.5(b)(1):

                  (1)      IF MEMBER SURVIVES TO BENEFIT COMMENCEMENT DATE.
                           The reduced amount of the monthly retirement
                           benefits payable to a terminated Member at
                           retirement (and accordingly under section 6.6, if

                                       -3-


<PAGE>   4



                           applicable), if he does not die prior to the Benefit
                           Commencement Date, shall be equal to an amount
                           determined by applying to the monthly retirement
                           benefit otherwise payable to the Member a "Reduction
                           Percentage" for the number of complete months during
                           which the coverage is in effect. The Reduction
                           Percentage shall be .0083 percent per month
                           (one-tenth of 1 percent per year) for Members under
                           age 45, .0333 percent per month (four-tenths of 1
                           percent per year) for Members ages 45 through 54, and
                           .0667 percent per month (eight-tenths of 1 percent
                           per year) for Members ages 55 through 64. On and
                           after October 1, 1994, the reduction described above
                           shall apply only with respect to individuals who are
                           Former Participants.

         IN WITNESS WHEREOF, the undersigned, a duly appointed member of the
Corporate Benefits Committee, has caused this Sixth Amendment to be executed on
its behalf, this _____ day of September, 1994.

                                       By
                                         ------------------------------
                                          A Member of the Corporate
                                          Benefits Committee

                                       -4-


<PAGE>   5



                              SEVENTH AMENDMENT TO
                              ROBBINS & MYERS, INC.
                                  PENSION PLAN

         WHEREAS, Robbins & Myers, Inc. (the "Company") maintains the Robbins &
Myers, Inc. Pension Plan (the "Plan"); and

         WHEREAS, amendment of the Plan is now deemed desirable;

         NOW, THEREFORE, the Corporate Benefits Committee, acting pursuant to
the authority granted to it by Section 11.1 of the Plan, hereby amend the Plan
is the follow particulars:

                  (1) By adding Addendum A, as attached hereto, immediately
         following the last Article thereof, effective for all distributions
         made after December 31, 1992.

                  (2) By adding Addendum B immediately following Addendum A as
         attached hereto, effective for all Plan Years beginning after December
         31, 1993.

         IN WITNESS WHEREOF, the undersigned, a duly appointed member of the
Corporate Benefits Committee, has caused this Seventh Amendment to be executed
on its behalf, this 23rd day of December, 1994.

                                       /s/
                                       ----------------------------------
                                       A Member of the Corporate Benefits
                                       Committee

                                       -5-


<PAGE>   6



                                   ADDENDUM A

                       IRS MODEL DIRECT ROLLOVER REVISIONS

A.1 ROLLOVER REQUIREMENTS

This Addendum applies to distributions made on or after January 1, 1993.
Notwithstanding any provision of the Plan to the contrary that would otherwise
limit a distributee's election under this Addendum, a distributee may elect, at
the time and in the manner prescribed by the plan administrator, to have any
portion of an eligible rollover distribution paid directly to an eligible
retirement plan specified by the distributee in a direct rollover.

A.2 DEFINITIONS

(a)      Eligible rollover distribution: An eligible rollover distribution is
         any cash distribution of all or any portion of the balance to the
         credit of the distributee, except that an eligible rollover
         distribution does not include: any distribution that is one of a series
         of substantially equal periodic payments (not less frequently than
         annually) made for the life (or life expectancy) of the distributee or
         the joint lives (or joint life expectancies) of the distributee and the
         distributee's designated beneficiary, or for a specified period of ten
         years or more; any distribution to the extent such distribution is
         required under Section 401(a)(9) of the Code; and the portion of any
         distribution that is not includible in gross income (determined without
         regard to the exclusion for net unrealized appreciation with respect to
         Employer securities).

(b)      Eligible retirement plan: An eligible retirement plan is an individual
         retirement account described in Section 408(a) of the Code, an
         individual retirement annuity described in Section 408(b) of the Code,
         an annuity plan described in Section 403(a) of the Code, or a qualified
         trust described in Section 401(a) of the Code, that accepts the
         distributee's eligible rollover distribution. However, in the case of
         an eligible rollover distribution to the surviving spouse, an eligible
         retirement plan is an individual retirement account or individual
         retirement annuity.

(c)      Distributee: A distributee includes an employee or former employee. In
         addition, the employee's or former employee's surviving spouse and the
         employee's or former employee's spouse or former spouse who is the
         alternate payee under a qualified domestic relations order, as defined
         in Section 414(p) of the Code, are distributees with regard to the
         interest of the spouse or former spouse.

                                       -6-


<PAGE>   7




(d)      Direct rollover: A direct rollover is a payment by the Plan to the
         eligible retirement plan specified by the distributee.

                                       -7-


<PAGE>   8



                                   ADDENDUM B

                      IRS MODEL SECTION 401(a)17 LIMITATION

In addition to other applicable limitations set forth in the plan, and
notwithstanding any other provision of the plan to the contrary, for plan years
beginning on or after January 1, 1994, the annual compensation of each employee
taken into account under the plan shall not exceed the OBRA '93 annual
compensation limit. The OBRA '93 annual compensation limit is $150,000, as
adjusted by the Commissioner for increases in the cost of living in accordance
with section 401(a)(17)(B) of the Internal Revenue Code. The cost-of-living
adjustment in effect for a calendar year applies to any period, not exceeding 12
months, over which compensation is determined (determination period) beginning
in such calendar year. If a determination period consists of fewer than 12
months, the OBRA '93 annual compensation limit will be multiplied by a fraction,
the numerator of which is the number of months in the determination period, and
the denominator of which is 12.

For plan years beginning on or after January 1, 1994, any reference in this plan
to the limitation under section 401(a)(17) of the Code shall mean the OBRA '93
annual compensation limit set forth in this provision.

If compensation for any prior determination period is taken into account in
determining an employee's benefit accruing in the current plan year, the
compensation for that prior determination period is subject to the OBRA '93
annual compensation limit in effect for that prior determination period. For
this purpose, for determination periods beginning before the first day of the
first plan year beginning on or after January 1, 1994, the OBRA '93 annual
compensation limit is $150,000.

                                       B-1


<PAGE>   9



                               EIGHTH AMENDMENT TO
                              ROBBINS & MYERS, INC.
                                  PENSION PLAN

         WHEREAS, Robbins & Myers, Inc. (the "Company") maintains the Robbins &
Myers, Inc. Pension Plan (the "Plan"); and

         WHEREAS, amendment of the Plan is now deemed desirable;

         NOW, THEREFORE, the Corporate Benefits Committee, acting pursuant to
the authority granted to it by Section 11.1 of the Plan, hereby amend the Plan,
effective October 1, 1993, by adding the following subsection 6.13 to the Plan:

         6.13 EXTENDED WEAR AWAY. Notwithstanding the foregoing, with respect to
each Participant whose Compensation exceeded $150,000 during the Plan Year ended
September 30, 1993, the amount of a Participant's Accrued Benefit will not be
less than the greater of the amount of the Participant's Accrued Benefit, if
any, determined as at September 30, 1989 under the terms of the Plan as then in
effect, or the amount of the Participant's Accrued Benefit, if any, determined
as at September 30, 1993 under the terms of the Plan as then in effect plus such
additional amount, if any, as is accrued after September 30, 1993 pursuant to
the foregoing provisions of this subsection.

         IN WITNESS WHEREOF, the undersigned, a duly appointed member of the
Corporate Benefits Committee, has caused this Eighth Amendment to be executed on
its behalf, effective as of September 30, 1994.

                                       /s/
                                       ----------------------------------
                                       A Member of the Corporate Benefits
                                       Committee

                                       B-2


<PAGE>   10



                               NINTH AMENDMENT TO
                              ROBBINS & MYERS, INC.
                                  PENSION PLAN

         WHEREAS, Robbins & Myers, Inc. (the "Company") maintains the Robbins &
Myers, Inc. Pension Plan (the "Plan"); and

         WHEREAS, amendment of the Plan is now deemed desirable;

         NOW, THEREFORE, the Corporate Benefits Committee, acting pursuant to
the authority granted to it by Section 11.1 of the Plan, hereby amend the Plan
effective October 1, 1989, in the follow particulars:

                  (1)  by adding the following two sentences to the end
         paragraph 2.1(j) of the Plan:

         If the Participant is a "5-percent owner" (as defined in section
         414(q)(3) of the Code) or is one of the 10 Highly Compensated Employees
         earning the most Compensation without regard to the $200,000 limit,
         such limitation shall be calculated by aggregating the Compensation of
         the Participant and of the Participant's spouse and his lineal
         descendents who have not attained age 19 by the close of the Plan Year,
         if they are Participants in the Plan. Compensation in excess of the
         limit under section 401(a)(17) shall not be taken into account under
         the Plan for any purpose.

                  (2) by adding the following two sentences to the end of
         paragraph 6.5(b)(1) of the Plan:

         There shall be no Reduction Percentage in effect for any month prior to
         the date the Committee provides notice to the Member of his and his
         spouse's rights to waive the preretirement surviving spouse annuity.

                  (3) by adding a new subsection 6.7(c) to the Plan:

                  (c) NORMAL FORM.  The qualified joint and survivor
         annuity described above shall be at least as valuable as any
         optional form of benefit payable under the Plan.

                  (4)  by inserting the word "any" at the end of the
         first line of subsection 6.8.

                  (5) by substituting the following for paragraphs 6.10(a) of
         the Plan:

                  6.10 MAXIMUM ANNUAL BENEFITS. Notwithstanding any other
         provisions of this Plan to the contrary, the annual

                                       B-3


<PAGE>   11



         benefit provided under this Plan (together with that provided by all
         other defined benefit plans of the Affiliates) for any Member for a
         limitation year, which shall be the calendar year, shall in no event
         exceed the lesser of (a) or (b) below:

         (a)      An amount equal to the lesser of (1) or (2) below:

                  (1)      $90,000, or the smaller Actuarial Equivalent of the
                           benefit payable at the Member's Social Security
                           Retirement Age if payments begin before that age, or
                           the larger Actuarial Equivalent of the benefit
                           payable at that age if payments begin after that age;
                           or

                  (2)      an amount equal to 100 percent of the annual
                           average of the highest three consecutive calendar
                           years of Compensation paid to him by the Employer
                           during his active participation in this Plan;
                           multiplied by the Member's Credited Service (or
                           his Vesting Service if subsection (a)(2) above is
                           applicable), determined as of the time benefits
                           commence, not to exceed ten years.  In no case
                           will the preceding limit reduce the accrued
                           benefit of a Member determined on September 30,
                           1983 or on September 30, 1987, provided such
                           benefit complied with the maximum benefit
                           limitation then in effect.

         If the Plan satisfied the applicable requirements of section 415 of the
         Code as in effect for all limitation years beginning before January 1,
         1987, an amount shall be subtracted from the numerator of the defined
         contribution plan fraction (not exceeding such numerator) as prescribed
         by the Secretary of the Treasury so that the sum of the defined benefit
         plan fraction and the defined contribution plan fraction computed under
         section 415(e)(1) of the Code, as revised by the Tax Reform Act of
         1986, does not exceed 1.0 for such limitation year. In the event the
         special limitation contained in this subparagraph is exceeded, the
         benefits otherwise payable to the Member under this qualified defined
         benefit Plan shall be reduced to the extent necessary to meet such
         limitation. If the annual benefit begins before a Member's Social
         Security Retirement Age, but on or after age 62, the actuarial
         adjustment for such benefit referred to in paragraph (1) above shall be
         determined by reducing the dollar limitation by five-ninths of 1
         percent for each of the first 36 months by which the Benefit
         Commencement Date precedes the Social Security Retirement Age, and by
         five-twelfths of 1 percent for each of the next 24 months, if any, by
         which the Benefit Commencement Date precedes the Social Security
         Retirement Age. For benefits commencing prior to age 62, an additional
         adjustment shall be made to the benefit which could otherwise have been
         payable commencing at age 62; such adjustment shall be based on an
         interest rate of 7 percent

                                       B-4


<PAGE>   12



         or such other rate described in section 2.1(b). If the annual benefit
         begins after a Member's Social Security Retirement Age, the actuarial
         adjustment for such benefit referred to in paragraph (1) above shall be
         based on an interest rate of 5 percent. If a Member's annual benefit
         does not exceed $10,000 and if he did not participate in any defined
         contribution plan maintained by an Affiliate, the limitations described
         in (1) and (2) above will not apply; provided, however, if such Member
         has fewer than ten years of Vesting Service, instead of $10,000, the
         exemption shall be $1,000 multiplied by his years of Vesting Service,
         determined as of the time benefits commence. The amount in (1) above,
         and the amount in (2) above for a Member who has terminated his
         employment with all Affiliates, shall be automatically adjusted
         annually for increases in the cost of living as follows: as of January
         1 of each calendar year, the dollar limitation as determined by the
         Commissioner of Internal Revenue for that calendar year will become
         effective as the maximum permissible dollar amount for that calendar
         year. The maximum permissible dollar amount for a calendar year applies
         to limitation years ending with or within that calendar year. The
         requirement of ten years of Vesting Service shall apply with respect to
         each change in benefit structure under the Plan, as required by section
         415(b)(5) of the Code and the regulations thereunder.

                  (6)  by adding a new subsection 6.14 to the Plan:

                  6.14 SPECIAL DISTRIBUTION RULES. All distributions required
         under this Plan shall be determined and made in accordance with
         Treasury Regulations under Code section 401(a)(9), including the
         minimum distribution incidental benefit requirement of Treasury
         Regulation section 1.401(a)(9)-2 and the provisions of section
         401(a)(11) of the Code relating to incidental death benefit payments.
         If the Participant dies after distribution of his or her interest has
         commenced, the remaining portion of such interest will continue to be
         distributed at least as rapidly as under the method of distribution
         being used prior to the Participant's death. If a Participant dies
         before distribution of his or her interest has commenced, distribution
         shall be made in accordance with the provisions of subsection
         401(a)(9)(B) of the Code.

                  (7)  by adding a new subsection 12.5 to the Plan:

                  12.5 AMENDMENT OF VESTING SCHEDULE. If the Plan is amended to
         provide a different vesting schedule, each person adversely affected:

                  (a)  who is a Participant during the election period
         below; and

                  (b)  who has completed at least three years of Service
         before that period ends;

                                       B-5


<PAGE>   13



         may elect to have the amendment disregarded in determining his vested
         amount. The election must be in writing and delivered to the Corporate
         Benefits Committee within the election period. Upon delivery, the
         election will be irrevocable. The election period begins on the date
         such amendment is adopted and ends 60 days after the latest of the
         date:

                  (c)      the amendment is adopted;

                  (d)      the amendment becomes effective; or

                  (e)      the Corporate Benefits Committee delivers a written
                           notice of the amendment to the Participant.

         No amendment to the Plan's vesting schedule may decrease the vested
         amount which any Participant has earned as of the date of the
         amendment.

                  (8)  by substituting the following for paragraph
         14.2(a) of the Plan:

         (a)      "AGGREGATION GROUP" means the Plan and all other plans
                  maintained by the Employer and nonparticipating
                  Affiliates which cover a Key Employee and any other
                  plan which enables a plan covering a Key Employee to
                  meet the requirements of Code section 401(a)(4) or 410
                  including any plan that terminated within the five-year
                  period ending on the relevant determination date.  In
                  addition, at the election of the Committee, the
                  Aggregation Group may be expanded to include any other
                  qualified plan maintained by an Employer or
                  nonparticipating Affiliate if such expanded Aggregation
                  Group meets the requirements of Code sections 401(a)(4)
                  and 410.

                  (9)  by substituting the following for subsection 14.3
         of the Plan:

                  14.3 VESTING REQUIREMENTS. If the Plan is determined to be
         top-heavy with respect to a Plan Year under the provisions of section
         14.1, then a Member's interest in his accrued benefit shall vest in
         accordance with the following schedule:

<TABLE>
<CAPTION>
                           Years of Service                   Vesting Percentage
                           ----------------                   ------------------
                           <S>                                        <C>
                           Less than 3                                  0%
                             3 or more                                100%
</TABLE>

         The vesting provisions described in this section shall not apply to a
         Member who does not have an Hour of Service after the Plan becomes
         top-heavy. If in a subsequent Plan Year the Plan is no longer
         top-heavy, the vesting provisions that

                                       B-6


<PAGE>   14



         were in effect prior to the time the Plan became top-heavy
         shall be reinstated.

                                       B-7


<PAGE>   15




         IN WITNESS WHEREOF, the undersigned, a duly appointed member of the
Corporate Benefits Committee, has caused this Ninth Amendment to be executed on
its behalf, this 12th day of June, 1996.

                                       /s/
                                       ----------------------------------
                                       A Member of the Corporate Benefits
                                       Committee

                                       B-8