GB1575784A - Method for the manufacture of a force transducer - Google Patents

Method for the manufacture of a force transducer Download PDF

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Publication number
GB1575784A
GB1575784A GB16462/78A GB1646278A GB1575784A GB 1575784 A GB1575784 A GB 1575784A GB 16462/78 A GB16462/78 A GB 16462/78A GB 1646278 A GB1646278 A GB 1646278A GB 1575784 A GB1575784 A GB 1575784A
Authority
GB
United Kingdom
Prior art keywords
rod
spring clip
cover
seismic
elements
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB16462/78A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hottinger Bruel and Kjaer AS
Original Assignee
Bruel and Kjaer AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bruel and Kjaer AS filed Critical Bruel and Kjaer AS
Publication of GB1575784A publication Critical patent/GB1575784A/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P21/00—Testing or calibrating of apparatus or devices covered by the preceding groups
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/16—Measuring force or stress, in general using properties of piezoelectric devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L23/00—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid
    • G01L23/22—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines
    • G01L23/221—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines for detecting or indicating knocks in internal combustion engines
    • G01L23/222—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines for detecting or indicating knocks in internal combustion engines using piezoelectric devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/09—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by piezoelectric pick-up
    • G01P15/0915—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by piezoelectric pick-up of the shear mode type

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
  • Force Measurement Appropriate To Specific Purposes (AREA)
  • Air Bags (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)

Description

(54) A METHOD FOR THE MANUFACTURE OF A FORCE TRANSDUCER (71) We, AKTIESELSKABET BRUEL & KJAER, a body corporate, organized under the laws of Denmark, of Linde Alle 23 DK-28So Naerum, Denmark, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: The invention concerns a method for the manufacture of a force transducer.
The force transducer consists of a base carrying a stud, a plurality of shear sensitive elements, each having a seismic and force transmitting mass associated with it, the masses being held against the shear sensitive elements, and the shear sensitive elements being held against the stud by means of a cylindrical spring clip surrounding the seismic and force transmitting masses, and a cover fitted to the base so as to surround the spring clip and carrying a plug for electrical connection to the shear sensitive elements. Force transducers of the kind described and used as accelerometers have been known for long and have many attractive features such as low temperature coefficient and low transverse sensitivity. The disadvantage inherent in this construction has been the cost of production which furthermore rose in inverse proportion to the size of the accelerometer. Thus, several instances are known where their use has been impossible through prohibitive costs. The production costs are mainly those of manual assembly as the parts may be efficiently produced on suitable machine tools.
It is a purpose of the invention to provide an improved method of manufacture of a force transducer of the kind described above, which method involves a minimum of manipulation.
According to the present invention there is provided a method of manufacture of a force transducer consisting of a base carrying a stud, a plurality of shear sensitive elements, each having a seismic and force transmitting mass associated with it, the masses being held against the shear sensitive elements, and the shear sensitive elements being held against the stud by means of a cylindrical spring clip surrounding the seismic and force transmitting masses, and a cover fitted to the base so as to surround the spring clip and carrying a plug for electrical connection to the shear sensitive elements, which method of manufacture includes the steps of: - 1) cutting slots parallel to the axis of a rod to one end thereof; the slots having a depth which is greater than the height of shear sensitive elements to be inserted therein, 2) inserting the shear sensitive elements into said slots, 3) fitting a cylindrical spring clip around the slotted part of the rod, and 4) cutting radially into the rod so as to remove the material making up the bottom of said slots to form seismic and force transmitting masses consisting of the parts of the rod material remaining between the spring dip and the elements, the steps to be taken in the order given.
The steps enumerated are well suited for being performed on an automatic lathe with attachments.
The invention will be described in detail in the following with reference to a particular force transducer, namely an accelerometer which is used in the example of the kind of force transducer intended. Reference is made to the accompanying drawing, in which: Figure 1 shows a perspective view of the component parts of an accelerorneter that may be manufactured either by known techniques or by the new technique taught by the present invention; and Figure 2 shows a rod in the various stages of the manufacture.
In Figure 1 the base 1 of the accelerometer is in one piece with a stud 2. A shear sensitive piezoelectric element 3 is disposed between the side of the stud 2 and a seismic mass 4. As there are three sets of piezoelectric element 3 and seismic mass 4 at 1200 from each other, the whole assembly is kept in place by means of a spring clip 5.
A cover 7 is fitted onto the base 1 and contains a coaxial electric plug 6 having electric contact fingers (not shown) which establish contact with the spring clip 5 or the seismic masses 4.
The technique used up to the present invention for the manufacture of the accelero meter as described above was the following: The base 1 with stud 2 is turned and milled from a piece of rod material. The shoulder for the cover 7 is turned and a hexagonal prism for a spanner is milled out of the base.
The base is cut off from the rod leaving a nipple which is subsequently threaded. The seismic masses 4 are obtained by milling, sawing, and grinding a second rod material.
The piezoelectric elements 3 are temporarily fixed to the stud 2 and the seismic masses 4 are temporarily fixed to the piezoelectric elements. In a suitable jig the spring clip 5 is pressed onto the temporary assembly.
Lastly, a cover 7 which has been prepared separately with coaxial plug 6 is pressed onto the recessed base 1. The technique described involves a considerable amount of manual assembly work which is particularly difficult in case the piezoelectric elements and the seismic masses have very small dimensions, such as is the case when the accelerometer is designed for a high upper frequency limit.
An alternative and advantageous technique according to the invention is as follows with reference to Figure 2 : - On an automatic lathe with associated tools a rod 8 is turned down to a diameter a which is suitable for the inside diameter of the cover 7. As shown at B and C three slots 9 are cut axially at a distance b from the axis of the rod. The depth of the cuts is somewhat larger than the height of the piezoelectric elements 3. At D it is shown how one of the piezo electric elements 3 is mounted in the slot 9 by pressing axially. At E it is shown how the spring clip 5 which has a continuous cylindrical surface is pressed down so that its rightmost (in the figure) end is at the same axial position as the piezoelectric elements 3.
At F it is shown that the bottoms of the slots 9 are removed by cutting at c to a suitable depth. Thus, the remaining pieces 4 become the seismic masses in the accelerometer when finished. The seismic masses and the piezo electric elements are now only held in place by means of the spring clip 5. In this manner a correct mounting of the various parts of an accelerometer has been obtained without involving manual work. The cover 7 which has been manufactured beforehand in a way not specified as it has no bearing on the invention is pressed onto the rod 8 as shown at G. In this way a contact spring 10 makes contact with the spring clip 5 and constitutes the centre connector of the coaxial electric plug 6 while the outer connector is made of the cover 7. The rod is cut at the rear end of the cover 7 leaving a nipple which is sub sequently threaded and the finished accelero meter is cut free from the rod as shown at H.
In one embodiment of the invention shown in Figure 1 the cover 7 is formed with a cylindric outer surface, and the rod is a hexagonal one, thus allowing a hexagonal spanner to be formed on the base 1.
In the embodiment shown in Figure 2 alternatively the cover 7 is provided with the hexagonal spanner and the rod is cut from a cylindric rod.
Above, the manufacture according to the invention has been described with reference to an accelerometer having three piezoelectric elements. There is, however, nothing that would prevent its use with e.g. two or a greater number of elements, it will only influence the geometry of the axial slots.
It is evident that although the invention has been disclosed with reference to an acolerometer, it is by no means limited to those, it may with equal advantage be applied to the manufacture of any force transducer of the construction described.
WHAT WE CLAIM IS:- 1. A method of manufacture of a force transducer consisting of a base carrying a stud, a plurality of shear sensitive elements, each having a seismic and force transmitting mass associated with it, the masses being held against the shear sensitive elements, and the shear sensitive elements being held against the stud by means of a cylindrical spring clip surrounding the seismic and force transmitting masses, and a cover fitted to the base so as to surround the spring clip and carrying a plug for electrical connection to the shear sensitive elements, which method of manufacture includes the steps of: - 1) cutting slots parallel to the axis of a rod with one end thereof; the slots having a depth which is greater than the height of shear sensitive elements to be inserted therein, 2) inserting the shear sensitive elements into said slots, 3) fitting a cylindrical spring clip around the slotted part of the rod, and 4) cutting radially into the rod so as to remove the material making up the bottom of said slots to form seismic and force trans
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

  1. **WARNING** start of CLMS field may overlap end of DESC **.
    mass 4. As there are three sets of piezoelectric element 3 and seismic mass 4 at 1200 from each other, the whole assembly is kept in place by means of a spring clip 5.
    A cover 7 is fitted onto the base 1 and contains a coaxial electric plug 6 having electric contact fingers (not shown) which establish contact with the spring clip 5 or the seismic masses 4.
    The technique used up to the present invention for the manufacture of the accelero meter as described above was the following: The base 1 with stud 2 is turned and milled from a piece of rod material. The shoulder for the cover 7 is turned and a hexagonal prism for a spanner is milled out of the base.
    The base is cut off from the rod leaving a nipple which is subsequently threaded. The seismic masses 4 are obtained by milling, sawing, and grinding a second rod material.
    The piezoelectric elements 3 are temporarily fixed to the stud 2 and the seismic masses
    4 are temporarily fixed to the piezoelectric elements. In a suitable jig the spring clip 5 is pressed onto the temporary assembly.
    Lastly, a cover 7 which has been prepared separately with coaxial plug 6 is pressed onto the recessed base 1. The technique described involves a considerable amount of manual assembly work which is particularly difficult in case the piezoelectric elements and the seismic masses have very small dimensions, such as is the case when the accelerometer is designed for a high upper frequency limit.
    An alternative and advantageous technique according to the invention is as follows with reference to Figure 2 : - On an automatic lathe with associated tools a rod 8 is turned down to a diameter a which is suitable for the inside diameter of the cover 7. As shown at B and C three slots 9 are cut axially at a distance b from the axis of the rod. The depth of the cuts is somewhat larger than the height of the piezoelectric elements 3. At D it is shown how one of the piezo electric elements 3 is mounted in the slot 9 by pressing axially. At E it is shown how the spring clip 5 which has a continuous cylindrical surface is pressed down so that its rightmost (in the figure) end is at the same axial position as the piezoelectric elements 3.
    At F it is shown that the bottoms of the slots
    9 are removed by cutting at c to a suitable depth. Thus, the remaining pieces 4 become the seismic masses in the accelerometer when finished. The seismic masses and the piezo electric elements are now only held in place by means of the spring clip 5. In this manner a correct mounting of the various parts of an accelerometer has been obtained without involving manual work. The cover 7 which has been manufactured beforehand in a way not specified as it has no bearing on the invention is pressed onto the rod 8 as shown at G. In this way a contact spring 10 makes contact with the spring clip 5 and constitutes the centre connector of the coaxial electric plug 6 while the outer connector is made of the cover 7. The rod is cut at the rear end of the cover 7 leaving a nipple which is sub sequently threaded and the finished accelero meter is cut free from the rod as shown at H.
    In one embodiment of the invention shown in Figure 1 the cover 7 is formed with a cylindric outer surface, and the rod is a hexagonal one, thus allowing a hexagonal spanner to be formed on the base 1.
    In the embodiment shown in Figure 2 alternatively the cover 7 is provided with the hexagonal spanner and the rod is cut from a cylindric rod.
    Above, the manufacture according to the invention has been described with reference to an accelerometer having three piezoelectric elements. There is, however, nothing that would prevent its use with e.g. two or a greater number of elements, it will only influence the geometry of the axial slots.
    It is evident that although the invention has been disclosed with reference to an acolerometer, it is by no means limited to those, it may with equal advantage be applied to the manufacture of any force transducer of the construction described.
    WHAT WE CLAIM IS:- 1. A method of manufacture of a force transducer consisting of a base carrying a stud, a plurality of shear sensitive elements, each having a seismic and force transmitting mass associated with it, the masses being held against the shear sensitive elements, and the shear sensitive elements being held against the stud by means of a cylindrical spring clip surrounding the seismic and force transmitting masses, and a cover fitted to the base so as to surround the spring clip and carrying a plug for electrical connection to the shear sensitive elements, which method of manufacture includes the steps of: - 1) cutting slots parallel to the axis of a rod with one end thereof; the slots having a depth which is greater than the height of shear sensitive elements to be inserted therein, 2) inserting the shear sensitive elements into said slots, 3) fitting a cylindrical spring clip around the slotted part of the rod, and 4) cutting radially into the rod so as to remove the material making up the bottom of said slots to form seismic and force trans
    mitting masses consisting of the parts of the rod material remaining between the spring clip and the elements, the steps to be taken in the order given.
  2. 2. A method for the manufacture of a force transducer substantially as hereinbefore described with reference to the accompanying drawings.
  3. 3. A force transducer manufactured by a method as claimed in either preceding claim.
GB16462/78A 1977-04-26 1978-04-26 Method for the manufacture of a force transducer Expired GB1575784A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DK181477AA DK139793B (en) 1977-04-26 1977-04-26 Method for manufacturing an electromechanical force meter.

Publications (1)

Publication Number Publication Date
GB1575784A true GB1575784A (en) 1980-09-24

Family

ID=8108249

Family Applications (1)

Application Number Title Priority Date Filing Date
GB16462/78A Expired GB1575784A (en) 1977-04-26 1978-04-26 Method for the manufacture of a force transducer

Country Status (5)

Country Link
JP (1) JPS5920104B2 (en)
DE (1) DE2817981C3 (en)
DK (1) DK139793B (en)
FR (1) FR2389113A1 (en)
GB (1) GB1575784A (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021244815A1 (en) 2020-06-02 2021-12-09 Kistler Holding Ag Acceleration sensor and use of such an acceleration sensor

Also Published As

Publication number Publication date
DE2817981C3 (en) 1980-09-25
FR2389113B3 (en) 1980-12-19
DK139793B (en) 1979-04-17
DE2817981B2 (en) 1980-01-24
JPS541075A (en) 1979-01-06
DK139793C (en) 1979-09-24
DK181477A (en) 1978-10-27
DE2817981A1 (en) 1978-12-07
JPS5920104B2 (en) 1984-05-10
FR2389113A1 (en) 1978-11-24

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Legal Events

Date Code Title Description
PS Patent sealed
PCNP Patent ceased through non-payment of renewal fee