1
                                                                 EXHIBIT 3.16
                         CERTIFICATE OF INCORPORATION
                                       OF
                                  IMPACT, INC.

        The undersigned, a natural person, for the purposes of organizing a
corporation for conducting the business and promoting the purposes hereinafter
stated, under the provisions and subject to the requirements of the laws of the
State of Delaware (particularly Chapter 1, Title 8 of the Delaware Code and the
acts amendatory thereof and supplemental thereto, and known, identified and
referred to as the "Delaware General Corporation Law"), hereby certifies that:

        FIRST:   The name of the corporation (hereinafter called the
"Corporation") is:

                                  IMPACT, INC.

        SECOND:  The address, including street, number, city and county of the
registered office of the Corporation in the State of Delaware is 32 Loockerman
Square Suite L-100, Dover, Delaware, Kent County and the name of the registered
agent of the Corporation in the State of Delaware at such address is The
Prentice-Hall Corporation System, Inc.

        THIRD:   The nature of the business and of the purposes to be conducted
and promoted by the Corporation shall be to engage in any lawful act or
activity for which corporations may be organized under the General Corporation
Law of the State of Delaware.

        FOURTH:  The total number of shares of stock which the Corporation
shall have the authority to issue is 1,000 shares $0.01 par value. Any and all
such shares issued, and for which the full consideration has been paid or
delivered, shall be deemed fully paid stock and the holder of such shares shall
not be liable for any further call or assessment or any other payment thereon.

        FIFTH:   The name and the mailing address of the sole incorporator is
as follows:

                    Name                      Mailing Address                   
                    ----                      ---------------
            Dianne M. Chiappetti            30 South Wacker Drive   
                                            Suite 2900              
                                            Chicago, Illinois 60606 
        
        SIXTH:   The books of the Corporation may be kept (subject to any
provision contained in the statutes) outside the State of Delaware at such
place or places as may be designated from time 
   2
to time by the Board of Directors or in the By-Laws of the Corporation.

        SEVENTH:  Whenever a compromise or arrangement is proposed between this
Corporation and its creditors or any class of them and/or between this
Corporation and its stockholders or any class of them, any court of equitable
jurisdiction within the State of Delaware may, on the application in a summary
way of this Corporation or of any creditor or stockholder thereof or on the
application of any receiver or receivers appointed for this Corporation under
the provisions of Section 291 of Title 8 of the Delaware Code or on the
application of trustees in dissolution or of any receiver or receivers
appointed for this Corporation under the provisions of Section 292 of Title 8
of the Delaware Code order a meeting of the creditors or class of creditors,
and/or of the stockholders or class of stockholders of this Corporation, as
the case may be, to be summoned in such manner as the said court directs. If a
majority in number representing three-fourths in value of the creditors or
class of creditors, and/or of the stockholders or class of stockholders of this
Corporation, as the case may be, agree to any compromise or arrangement and to
any reorganization of this Corporation as a consequence of such compromise or
arrangement, the said compromise or arrangement and the said reorganization
shall, if sanctioned by the court to which the said application has been made,
be binding on all the creditors or class of creditors, and/or of the
stockholders or class of stockholders of this Corporation as the case may be,
and also on this Corporation.

        EIGHTH:  For the management of the business and for the conduct of the
affairs of the Corporation and in further definition, limitation and regulation
of the powers of the Corporation and of its directors and stockholders, it is
further provided:

1.      The number of directors of the Corporation shall be as specified in the
        By-Laws of the Corporation but such number may from time to time be
        increased or decreased in such manner as may be prescribed by the
        By-Laws. In no event shall the number of directors be less than the
        minimum prescribed by law. The election of directors need not be by
        ballot. Directors need not be stockholders.

2.      In furtherance and not in limitation of the powers conferred by the
        laws of the State of Delaware, the Board of Directors is expressly
        authorized and empowered to make, alter, amend, and repeal By-Laws,
        subject to the power of the stockholders to alter or repeal By-Laws
        made by the Board of Directors.

3.      Any director or any officer elected or appointed by the stockholders or
        by the Board of Directors may be removed at 


                                      -2-
   3
        any time in such manner as shall be provided in the By-Laws of the 
        Corporation.

4.      In the absence of fraud, no contract or other transaction between the
        Corporation and any other corporation and no act of the Corporation,
        shall in any way be affected or invalidated by the fact that any of the
        directors of the Corporation are pecuniarily or otherwise interested
        in, or are directors or officers of, such other corporation; and in the
        absence of fraud, any director, individually, or any firm of which any
        director may be a member, may be a party to, or may be pecuniarily or
        otherwise interested in, any contract or transaction of the
        Corporation; provided, in any case, that the fact that he or such firm
        is so interested shall be disclosed or shall have been known to the
        Board of Directors or the majority thereof; and any director of the
        Corporation, who is also a director or officer of any such other
        corporation, or who is also interested, may be counted in determining
        the existence of a quorum at any meeting of the Board of Directors of
        the Corporation which shall authorize any such contract, act or
        transaction, and may vote thereat to authorize any such contract, act
        or transaction, with like force and effect as if he were not such
        director or officer of such other corporation, or not so interested.

5.      To the fullest extent permitted by the Delaware General Corporation Law
        as it now exists or may hereafter be amended, no director of this
        Corporation shall be liable to this Corporation or any of its
        stockholders for monetary damages for breach of fiduciary duty as a
        director.

        NINTH:  (a)  Any person who was or is a party or is threatened to be
made a party to any threatened, pending or completed action, suit or
proceeding, whether civil, criminal, administrative or investigative
(hereinafter a "proceeding"), by reason of the fact that he or she, or a person
of whom he or she is the legal representative, is or was a director, officer,
employee or agent of the Corporation or is or was serving at the request of the
Corporation as a director, officer, employee or agent of another corporation or
of a partnership, joint venture, trust or other enterprise, including service
with respect to employee benefit plans, whether the basis of such proceeding is
alleged action in an official capacity as a director, officer, employee or agent
or in any other capacity while serving as a director, officer, employee or
agent, may be indemnified and held harmless by the Corporation to the fullest
extent authorized by and in the manner set forth in the Delaware General
Corporation Law against all expense, liability and loss (including attorneys'
fees, judgments, fines, ERISA excise taxes or penalties and amounts paid or to
be paid in settlement) reasonably incurred or suffered by such person in
connection therewith and such 



                                      -3-
   4
indemnification shall continue as to a person who has ceased to be a director,
officer, employee or agent and shall inure to the benefit of his or her heirs,
executors and administrators; provided, however, that, except as provided in
subsection (b) of this Article NINTH, the Corporation may indemnify any such
person seeking indemnification in connection with a proceeding (or part
thereof) initiated by such person only if such proceeding (or part thereof) was
authorized by the Board of Directors of the Corporation. Any right to
indemnification conferred by the Corporation pursuant to this Article NINTH may
include the right to be paid by the Corporation the expenses incurred in
defending any such proceeding in advance of its final disposition; provided,
however, that, if the Delaware General Corporation law requires, the payment of
such expenses incurred by a director or officer in his or her capacity as a
director or officer (and not in any other capacity in which service was or is
rendered by such person while a director or officer, including, without
limitation, service to an employee benefit plan) in advance of the final
disposition of a proceeding, shall be made only upon delivery to the
Corporation of an undertaking, by or on behalf of such director or officer, to
repay all amounts so advanced if it shall ultimately be determined that such
director or officer is not entitled to be indemnified under this Article or
otherwise.

        (b)   If any claim arising from any right to indemnification
conferred by the Corporation pursuant to the authority granted under subsection
(a) of this Article NINTH is not paid in full by the Corporation within thirty
days after a written claim has been received by the Corporation, the claimant
may at any time thereafter bring suit against the Corporation to recover the
unpaid amount of the claim and, if successful in whole or in part, the claimant
shall be entitled to be paid also the expense of prosecuting such claim. It
shall be a defense to any such action (other than an action brought to enforce
a claim for expenses incurred in defending any proceeding in advance of its
final disposition where the required undertaking, if any is required, has been
tendered to the Corporation) that the claimant has not met the standards of
conduct which make it permissible under the Delaware General Corporation Law
for the Corporation to indemnify the claimant for the amount claimed. Neither
the failure of the Corporation (including its Board of Directors, independent
legal counsel, or its stockholders) to have made a determination prior to the
commencement of such action that indemnification prior to the commencement of
such action that indemnification of the claimant is proper in the circumstances
because he or she has met the applicable standard of conduct set forth in the
Delaware General Corporation Law, nor an actual determination by the
Corporation (including its Board of Directors, independent legal counsel, or its
stockholders) that the claimant has not met such applicable standard or
conduct, shall be a defense to the action or create a presumption that the
claimant has not met the applicable standard of conduct.




                                      -4-
   5
        (c)     The right to indemnification and the payment of expenses
incurred in defending a proceeding in advance of its final disposition
authorized by this Article shall not be exclusive of any other right which any
person may have or hereafter acquire under any statute, provision of this
Certificate of Incorporation, by-law, agreement, vote of stockholders or
disinterested directors or otherwise.

        (d)     The Corporation amy maintain insurance, at its expense, to
protect itself and any director, officer, employee or agent of the Corporation
or another corporation, partnership, joint venture, trust or other enterprise
against any such expense, liability or loss, whether or not the Corporation
would have the power to indemnify such person against such expense, liability
or loss under the Delaware General Corporation Law.

        (e)     For the purposes of this Article, references to "the
Corporation" include, in addition to the resulting corporation, any constituent
corporation (including any constituent of a constituent) absorbed in a
consolidation or merger which, if its separate existence had continued, would
have had power and authority to indemnify its directors, officers and employees
or agents, so that nay person who is or was serving at the request of such
constituent corporation as a director, officer, employee or agent of another
corporation or is or was serving at the request of such constituent corporation
as a director, officer, employee or agent of another corporation, partnership,
joint venture, trust or other enterprise, shall stand in the same position under
the provisions of this Article with respect to the resulting or surviving
corporation if its separate existence had continued.

        For the purposes of this Article, references to "other enterprises"
shall include employee benefit plans; references to "fines" shall include any
excise taxes assessed on a person with respect to any employee benefit plan;
and references to "serving at the request of the Corporation" shall include any
service as a director, officer, employee or agent of the Corporation which
imposes duties on, or involves services by, such director, officer employee, or
agent with respect to an employee benefit plan, its participants or
beneficiaries; and a person who acted in good faith and in a manner he
reasonably believed to be in the interest of the participants and beneficiaries
of an employee benefit plan shall be deemed to have acted in a manner "not
opposed to the best interests of the Corporation" as referred to in this
Article.

        TENTH:  From time to time any of the provisions of this Certificate of
Incorporation may be amended, altered or repealed, and other provisions
authorized by the laws of the State of Delaware at the time in force may be
added or inserted in the 


                                      -5-
   6
manner and at the time prescribed by said laws, and all rights at any time
conferred upon the stockholders of the Corporation by this Certificate are
granted subject to the provisions of this Article TENTH.

Executed at Chicago, Illinois on the 1st day of November, 1993.


                                        /s/ DIANNE M. CHIAPPETTI
                                        ------------------------------
                                        Dianne M. Chiappetti
                                        Incorporator




                                      -6-