Positioning and clamping device

Abstract

The utility model relates to the field of positioning clamps, in particular to a positioning and clamping device which comprises a pressing head, a bolt, an air cylinder and an integral support. Wherein the pressing head is configured to be movably connected relative to the integral support, the moving direction of the pressing head is the vertical direction, the bolt and the integral support are configured to be adjustably connected, the moving direction of the bolt is the vertical direction, and the pressing head, the piston rod and the bolt are configured to be coaxial; the thermocouple is positioned through the pressure head and the bolt, and the cylinder continuously provides downward driving force along the vertical direction and transmits the driving force to the thermocouple through the pressure head, so that the glass powder filled between the porcelain tubes of the thermocouple is extruded into gaps between the porcelain tubes and between the porcelain tubes and the metal shell after being melted at high temperature. And the glass body formed by melting and cooling the glass powder is densely distributed in the gaps between the porcelain tubes and between the porcelain tubes and the metal shell, so that the bonding effect between the porcelain tubes and between the porcelain tubes and the metal shell is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to positioning fixture field, concretely relates to a positioning clamping device. BACKGROUND

[0002] The assembled thermocouple is a kind of relatively traditional thermocouple product, due to the excellent characteristics of the type thermocouple, such as fast response time, high precision, simple structure, wide temperature measurement range, stable process performance, it has been widely used in the temperature measurement field of aviation, aerospace etc.The common structure of assembled thermocouple, as shown in Figure Figure 1 The shell of metal material, 2 porcelain tubes, 3 glass powder, at least 2 porcelain tubes and 2 porcelain tubes are filled with 3 glass powder, the part filled with glass powder is inductively heated using high-frequency induction sintering device to melt glass powder, after cooling, the porcelain tube and the porcelain tube between the porcelain tube and the shell are bonded together.Current high-frequency induction sintering device has the following problems in the sintering process: after the glass powder melts and cools into glass body, the volume will greatly reduce, there will be more gaps in the space originally filled with glass between the porcelain tube and the porcelain tube, resulting in unsatisfactory bonding effect. CONTENT OF THE UTILITY MODEL

[0003] To solve the above technical problems, the utility model provides a positioning clamping device.

[0004] The utility model discloses the following technical scheme realizes:

[0005] A positioning clamping device, including pressure head, bolt, cylinder and overall support;

[0006] The pressure head, the bolt and the cylinder are arranged on the overall support respectively, wherein the pressure head is configured to be movably connected relative to the overall support, the movement direction of the pressure head is vertical direction, the bolt is configured to be adjustably connected with the overall support, the movement direction of the bolt is vertical direction, the cylinder includes cylinder body and piston rod, the cylinder body is configured to be fixedly connected with the overall support, the overall support is provided with first hole, the piston rod can pass through the first hole, the outer diameter of the piston rod is less than the inner diameter of the first hole, and the movement direction of the piston rod is vertical direction;

[0007] The pressure head, the piston rod and the bolt are coaxial, and the pressure head is located between the piston rod and the bolt;

[0008] The piston rod has first state and second state, the piston rod in the first state is not in contact with the pressure head, and the piston rod in the second state provides the pressure head with driving force in vertical direction downward.

[0009] Further, the whole bracket further comprises a first connecting plate, the first connecting plate is fixedly connected with the whole bracket, and a second hole is arranged on the first connecting plate and located below the first hole;

[0010] The top rod has a head end and a tail end, the head end is provided with a protruding part protruding along the radial direction of the top rod, the top rod is sleeved with the compression spring, the inner diameter of the compression spring is smaller than the outer diameter of the protruding part, the compression spring is limited above the first connecting plate, the tail end of the top rod is arranged in the second hole, the inner diameter of the second hole is greater than the outer diameter of the top rod, and the tail end of the top rod is fixedly or detachably connected with the pressure head, and the piston rod in the second state is in close contact with the head end.

[0011] Further, the whole bracket further comprises a first connecting plate, the first connecting plate is fixedly connected with the whole bracket, and a second hole is arranged on the first connecting plate and located below the first hole;

[0012] Further, the whole bracket further comprises a first connecting plate, the first connecting plate is fixedly connected with the whole bracket, and a second hole is arranged on the first connecting plate and located below the first hole;

[0013] Further, the whole bracket further comprises a first connecting plate, the first connecting plate is fixedly connected with the whole bracket, and a second hole is arranged on the first connecting plate and located below the first hole;

[0014] The left side plate, the right side plate and the middle plate jointly limit an installation area, and the installation area is used for arranging a coil.

[0015] Further, the middle plate, the cover sheet, the left side plate and the right side plate are all made of brass.

[0016] Further, the whole bracket further comprises a first connecting plate, the first connecting plate is fixedly connected with the whole bracket, and a second hole is arranged on the first connecting plate and located below the first hole;

[0017] The positioning and clamping device provided by the utility model positions the thermocouple through the pressure head and the bolt, continuously provides the driving force along the vertical direction by the air cylinder and transmits the driving force to the thermocouple through the pressure head, so that the two ends of the thermocouple along the vertical direction are always subjected to the pressure along the vertical direction in the sintering process, the glass powder filled between the porcelain tubes and extruded into the gap between the porcelain tubes and the metal shell after high-temperature melting, and the glass body formed after the glass powder is cooled is densely distributed in the gap between the porcelain tubes and the metal shell, thereby improving the bonding effect between the porcelain tubes and the metal shell. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the specific embodiments of the utility model, the drawings needed in the specific embodiments will be briefly introduced as follows. Obviously, the drawings described in the following are some embodiments of the utility model, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0019] Figure 1 It is a structural schematic view of the assembled thermocouple assembly in the prior art.

[0020] Figure 2 It is a structural schematic view of the positioning and clamping device provided by the embodiment 1 of the utility model.

[0021] Figure 3 It is a structural schematic view of the middle baffle and the cover sheet provided by the embodiment 1 of the utility model.

[0022] In the drawing, the marks are as follows: shell 1, porcelain tube 2, glass powder 3, air cylinder 4, cylinder body 5, pressure head 6, integral support 7, first connecting plate 8, second connecting plate 9, bolt 10, compression spring 11, top rod 12, bushing 13, first nut 14, middle baffle 15, cover sheet 16, upper surface 17, mounting groove 18, supporting surface 19, left side plate 20, right side plate 21, connecting rod 22, first hole 23, second hole 24, sintering support 25, protruding part 26, vertical direction A, horizontal direction B, inlet pipeline C of compressed air. DETAILED DESCRIPTION

[0023] The content of the utility model will be described clearly and completely in combination with the drawings. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Other embodiments obtained by those skilled in the art without creative labor on the basis of the embodiments in the utility model all belong to the protection scope of the utility model.

[0024] Embodiment 1

[0025] As Figures 2-3 shown, the embodiment is a preferred embodiment of the utility model, and the embodiment provides a positioning and clamping device which comprises a pressure head 6, a bolt 10, a gas cylinder 4 and a whole bracket 7;

[0026] The pressure head 6, the bolt 10 and the gas cylinder 4 are arranged on the whole bracket 7, wherein the pressure head 6 is movably connected to the whole bracket 7, the movement direction of the pressure head 6 is the vertical direction, the bolt 10 is adjustably connected to the whole bracket 7, the movement direction of the bolt 10 is the vertical direction, the gas cylinder 4 comprises a cylinder body 5 and a piston rod (not shown in the figure), the cylinder body 5 is fixedly connected to the whole bracket 7, the whole bracket 7 is provided with a first hole 23, the piston rod can pass through the first hole 23, the outer diameter of the piston rod is smaller than the inner diameter of the first hole 23, and the movement direction of the piston rod is the vertical direction;

[0027] The pressure head 6, the piston rod and the bolt 10 are coaxial, and the pressure head 6 is located between the piston rod and the bolt 10;

[0028] The piston rod has a first state and a second state, the piston rod in the first state is not in contact with the pressure head 6, and the piston rod in the second state provides the pressure head 6 with a driving force in the vertical direction downward.

[0029] The structure of the gas cylinder 4 is common knowledge known by those skilled in the art, and specifically comprises the cylinder body 5 and the piston rod, when the piston rod is in the first state, the pressure head 6 and the bolt 10 are not clamped with the thermocouple, and the piston rod is not in contact with the pressure head 6; when the piston rod is in the second state, compressed air is continuously introduced into the cylinder body 5, so that the piston rod continuously provides the pressure head 6 with the driving force in the vertical direction downward under the action of the compressed air, so that the two ends of the thermocouple along the vertical direction are clamped between the pressure head 6 and the bolt 10, and then the two ends of the thermocouple along the vertical direction are always subjected to the pressure along the vertical direction.

[0030] Further, the positioning and clamping device in the embodiment further comprises a top rod 12 and a compression spring 11, and the whole bracket 7 further comprises a first connecting plate 8, the first connecting plate 8 is fixedly connected to the whole bracket 7, the first connecting plate 8 is provided with a second hole 24, and the second hole 24 is located below the first hole 23;

[0031] The top rod 12 has a head end and a tail end, the head end is provided with a protrusion 26 protruding along the radial direction of the top rod, the top rod 12 is sleeved with a compression spring 11, the inner diameter of the compression spring 11 is smaller than the outer diameter of the protrusion 26, the compression spring 11 is limited above the first connecting plate 8, the tail end of the top rod 12 is arranged in the second hole 24, the inner diameter of the second hole 24 is larger than the outer diameter of the top rod 12, the tail end of the top rod 12 is fixedly or detachably connected with the pressure head 6, and the piston rod in the second state is in close contact with the head end. The top rod 12 is in clearance fit with the second hole 24 of the first connecting plate 8, when the piston rod is in the second state, the piston rod moves downward along the vertical direction through the top rod 12, continuously drives the pressure head, so that the top rod 12 drives the pressure head 6 to move downward, at this time, the distance between the two ends of the compression spring 11 is reduced, when the piston rod changes from the second state to the first state, the distance between the two ends of the compression spring 11 gradually increases, and the elastic force of the compression spring 11 drives the top rod 12 and the pressure head 6 to gradually move upward along the vertical direction.

[0032] Further, the positioning and clamping device in the embodiment further comprises a bushing 13 and a first nut 14, the head end of the bushing 13 is sleeved into the second hole 24, the bushing 13 and the top rod 12 are coaxial and in clearance fit, the connecting end of the bushing 13 is provided with external threads, and the internal threads of the first nut 14 are connected with the external threads.

[0033] The bushing 13 is coaxial and in clearance fit with the top rod 12, specifically, the bushing 13 is sleeved on the top rod 12, clearance fit is formed between the bushing 13 and the top rod 12, so that the top rod 12 and the bushing 13 form a sliding pair; the bushing 13 can reduce the wear of the top rod 12 during the vertical movement of the top rod 12 relative to the first connecting plate 8, and the bushing 13 plays a guiding role in the vertical movement of the top rod 12; the first nut 14 plays a role of fixing the bushing 13 on the first connecting plate 8.

[0034] Further, the positioning and clamping device in the embodiment further comprises a sintering support 25, the sintering support 25 is located between the pressure head 6 and the bolt 10, the sintering support 25 comprises a middle baffle 15 and a cover plate 16, the middle baffle 15 is fixedly connected with the integral support 7, the middle baffle 15 has an upper surface 17, the middle baffle 15 has a mounting groove 18, the mounting groove 18 is recessed in the upper surface 17, the cover plate 16 is arranged in the mounting groove 18, the cover plate 16 has a supporting surface 19, the supporting surface 19 is flush with the upper surface 17, the cover plate 16 protrudes from the middle baffle 15 along the horizontal direction, and the horizontal direction is perpendicular to the vertical direction.

[0035] It should be understood that the sintering support 25 is a mounting position of a coil (not shown in the figure), and it is common knowledge for those skilled in the art to use a coil to perform high-frequency induction sintering on the glass powder 3 in the thermocouple.

[0036] Further, the overall support 7 of the positioning and clamping device in the embodiment further comprises a second connecting plate 9, the sintering support 25 further comprises a left side plate 20 and a right side plate 21, the second connecting plate 9 is fixedly connected with the overall support 7, the middle baffle 15 is located above the second connecting plate 9, the second connecting plate 9 is provided with an inner threaded hole, the center line of the inner threaded hole is limited to be parallel to the vertical direction, and the bolt 10 is arranged in the inner threaded hole;

[0037] The left side plate 20, the right side plate 21 and the middle baffle 15 jointly limit an installation area, and the installation area is arranged to be used for arranging a coil.

[0038] When the thermocouple is heated in a high-frequency induction mode, the coil can be placed in the installation area, so that the coil is coaxial with the thermocouple.

[0039] Further, the middle baffle 15, the cover plate 16, the left side plate 20 and the right side plate 21 of the positioning and clamping device in the embodiment are all made of brass.

[0040] The brass can still maintain high strength and hardness at high temperature and has good heat conduction effect.

[0041] Further, the positioning and clamping device in the embodiment further comprises a connecting rod 22, when the piston rod is in the second state, the connecting rod 22 is limited between the pressure head 6 and the bolt 10, the connecting rod 22 is coaxial with the pressure head 6 and the bolt 10 respectively, and one end of the connecting rod 22 is in contact with the pressure head 6. It should be understood that the clamping of thermocouples of different sizes in the embodiment can be realized by adjusting the distance of the bolt 10 relative to the pressure head 6, specifically, a first mode is to keep the current position of the pressure head 6 unchanged, adjust the position of the bolt 10 relative to the second connecting plate 9, so that the bolt 10 generates a movement trend along the vertical direction, thereby adjusting the distance between the pressure head 6 and the bolt 10; a second mode is to keep the current position of the bolt 10 unchanged, control the air pressure input into the cylinder 5, so that the piston rod drives the pressure head to generate a movement trend along the vertical direction through the aforementioned top rod, thereby adjusting the distance between the pressure head 6 and the bolt 10;

[0042] If the size of the thermocouple is smaller than the minimum size of the thermocouple that can be clamped by the pressure head 6 and the bolt 10, it means that even if the thermocouple is arranged between the pressure head 6 and the bolt 10, and the piston rod of the cylinder 4 is driven to the limit position along the vertical direction downward, and the limit position of the bolt 10 relative to the second connecting plate 9 in the vertical direction upward is adjusted, the thermocouple at this time cannot be clamped by the pressure head 6 and the bolt 10, because the distance between the pressure head 6 at the limit position and the bolt 10 at the limit position at this time is greater than the length of the thermocouple arranged along the vertical direction; therefore, when the size of the thermocouple is smaller than the minimum size of the thermocouple that can be clamped by the pressure head 6 and the bolt 10, the connecting rod 22 is used as an extension or a spacer of the pressure head 6 in the embodiment, so that the connecting rod 22 and the thermocouple are clamped together by the pressure head 6 and the bolt 10.

[0043] The use process of the utility model is as follows:

[0044] When the piston rod is in the first state, the piston rod is not in contact with the jacking rod 12; the air source introduces compressed air into the cylinder body 5, so that the piston rod has a downward movement trend along the vertical direction under the action of the compressed air, and then the piston rod contacts the jacking rod 12; the piston rod is in close contact with the jacking rod 12, so that the jacking rod 12 is driven by the piston rod to have a downward movement trend along the vertical direction, until the distance between the pressure head 6 and the bolt 10 is slightly greater than the size of the thermocouple in the vertical direction, at this time, the distance between the pressure head 6 and the bolt 10 is convenient for the thermocouple to be vertically inserted into the position between the pressure head 6 and the bolt 10;

[0045] Then, after the thermocouple is vertically inserted between the pressure head 6 and the bolt 10 by using the clamping tool, the distance between the bolt 10 and the pressure head 6 is adjusted, so that the distance between the bolt 10 and the pressure head 6 is shortened, so that the thermocouple in the vertical state is clamped by the pressure head 6 and the bolt 10 in the vertical direction; specifically, the first mode is to keep the current position of the pressure head 6 unchanged, and adjust the position of the bolt 10 relative to the second connecting plate 9, so that the bolt 10 has a movement trend along the direction from the bolt 10 to the pressure head 6, thereby shortening the distance between the pressure head 6 and the bolt 10; the second mode is to keep the current position of the bolt 10 unchanged, and increase the air pressure continuously introduced into the cylinder body 5, so that the piston rod drives the pressure head 6 to have a movement trend along the direction from the pressure head 6 to the bolt 10 through the jacking rod 12, thereby shortening the distance between the pressure head 6 and the bolt 10;

[0046] If the size of the thermocouple is smaller than the minimum size of the thermocouple that can be clamped by the pressure head 6 and the bolt 10, it means that even if the thermocouple is arranged between the pressure head 6 and the bolt 10, and the piston rod of the cylinder 4 is driven to the limit position along the vertical direction downward, and the limit position of the bolt 10 relative to the second connecting plate 9 in the vertical direction upward is adjusted, the thermocouple at this time cannot be clamped by the pressure head 6 and the bolt 10, because the distance between the pressure head 6 in the limit position and the bolt 10 in the limit position is greater than the length of the thermocouple arranged along the vertical direction; therefore, the connecting rod 22 needs to be used as an extension or spacer of the pressure head 6, so that the connecting rod 22 and the thermocouple are clamped together by the pressure head 6 and the bolt 10; before the piston rod of the cylinder 4 is driven to the limit position along the vertical direction downward, and the limit position of the bolt 10 relative to the second connecting plate 9 in the vertical direction upward is adjusted, the thermocouple arranged between the pressure head 6 and the bolt 10 is shortened by the connecting rod 22, the distance between the thermocouple and the pressure head 6, or the distance between the thermocouple and the bolt 10, so that the pressure head 6 and the bolt 10 can clamp the connecting rod 22 and the thermocouple.

[0047] At the position of the sintering support 25, the thermocouple is heated to form sintering of the thermocouple, and at this time the piston rod is in the second state; during the heating of the thermocouple, the glass powder 3 in the thermocouple gradually melts, and at the same time the cylinder body 5 of the cylinder 4 is always supplied with compressed gas, and the driving force along the vertical direction is continuously provided by the piston rod of the cylinder 4 and transmitted to the thermocouple through the pressure head 6, so that the two ends of the thermocouple along the vertical direction are always subjected to pressure along the vertical direction during sintering, so that the glass powder 3 filled between the porcelain tubes 2 is extruded into the gap between the porcelain tubes 2 and the porcelain tubes 2, and the porcelain tubes 2 and the metal shell 1 after high-temperature melting.

[0048] After the glass powder 3 in the thermocouple is completely melted, the sintering heating process is stopped, at this time, the molten glass in the thermocouple is changed from the heated state to the cooling state, that is, the temperature of the molten glass in the thermocouple gradually decreases; in this process, as the temperature of the glass gradually decreases, the volume of the glass decreases, but the glass at this time still remains in the molten state, therefore, the driving force along the vertical direction is continuously provided by the piston rod of the air cylinder 4 and is transmitted to the thermocouple through the pressure head 6, so that the two ends of the thermocouple along the vertical direction are always subjected to the pressure along the vertical direction during the cooling process, resulting in that even if the glass cools to form a gap, the gap is still filled with the glass in the molten state due to the mutual extrusion of the porcelain tubes 2 and the porcelain tubes 2 or the mutual extrusion of the porcelain tubes 2 and the metal shell 1 under the pressure of the two ends of the thermocouple, until the glass cools to the solid state; through the above-mentioned heating mode of extruding the thermocouple, the gap between the porcelain tubes 2 and the porcelain tubes 2 is reduced, the gap between the porcelain tubes 2 and the metal shell 1 is reduced, the bonding effect between the porcelain tubes 2 and the porcelain tubes 2 is improved, and the bonding effect between the porcelain tubes 2 and the metal shell 1 is improved; after the glass in the molten state in the thermocouple is completely cooled to form a glass body, the piston rod is controlled by the air cylinder 4 to move upward along the vertical direction, and the thermocouple is taken out by the clamping tool, so that the thermocouple is away from the sintering support 25 position, if the connecting rod 22 is used during the sintering process, the thermocouple and the connecting rod 22 are taken out together; the piston rod is controlled by the air cylinder 4 to move upward along the vertical direction until the piston rod reaches the first state, and the air cylinder 4 stops the movement of the piston rod; in this process, the compression spring 11 rebounds, and the elastic force of the compression spring 11 drives the top rod 12 and the pressure head 6 to move upward along the vertical direction; when the piston rod reaches the first state again, the piston rod and the top rod 12 are not in contact.

[0049] The positioning and clamping device provided by the utility model positions the thermocouple through the pressure head and the bolt, continuously provides driving force along the vertical direction by the air cylinder and transmits the driving force to the thermocouple through the pressure head, so that the two ends of the thermocouple along the vertical direction are always subjected to pressure along the vertical direction during the sintering process, so that the glass powder filled between the porcelain tubes of the thermocouple is extruded into the gap between the porcelain tubes and the porcelain tubes or between the porcelain tubes and the metal shell after high-temperature melting, so that the glass body formed after the glass powder cools and melts is densely distributed in the gap between the porcelain tubes and the porcelain tubes or between the porcelain tubes and the metal shell, thereby improving the bonding effect between the porcelain tubes and the porcelain tubes or between the porcelain tubes and the metal shell.

[0050] Obviously, the above embodiments are only examples for clearly illustrating, but not limit the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the utility model.

Claims

1. A positioning and clamping device, characterized in that The pressure head, the bolt, the cylinder and the integral support are provided on the integral support respectively, wherein the pressure head is movably connected to the integral support in a vertical direction, the bolt is adjustably connected to the integral support in a vertical direction, the cylinder comprises a cylinder body and a piston rod, the cylinder body is fixedly connected to the integral support, the integral support is provided with a first hole, the piston rod can pass through the first hole, the outer diameter of the piston rod is smaller than the inner diameter of the first hole, and the piston rod moves in a vertical direction. The pressure head, the piston rod and the bolt are coaxial, and the pressure head is located between the piston rod and the bolt. The piston rod has a first state and a second state, the piston rod in the first state is not in contact with the pressure head, and the piston rod in the second state provides the pressure head with a driving force in a vertical downward direction. The integral support further comprises a first connecting plate, the first connecting plate is fixedly connected to the integral support, the first connecting plate is provided with a second hole, and the second hole is located below the first hole.

2. A positioning and clamping device according to claim 1, characterized in that The top rod has a head end and a tail end, the head end is provided with a protruding part protruding in a radial direction of the top rod, the top rod is sleeved with a compression spring, the inner diameter of the compression spring is smaller than the outer diameter of the protruding part, the compression spring is limited above the first connecting plate, the tail end of the top rod is arranged in the second hole, the inner diameter of the second hole is greater than the outer diameter of the top rod, and the tail end of the top rod is fixedly or detachably connected to the pressure head. The piston rod in the second state is in close contact with the head end.

3. A positioning and clamping device according to claim 2, characterized in that The integral support further comprises a bushing and a first nut, the head end of the bushing is inserted into the second hole, the bushing and the top rod are coaxial and clearance-fitted, the tail end of the bushing is provided with external threads, and the internal threads of the first nut are connected to the external threads.

4. The positioning and clamping device according to claim 1, characterized in that The integral support further comprises a sintering support, the sintering support is located between the pressure head and the bolt, the sintering support comprises a middle baffle and a cover piece, the middle baffle is fixedly connected to the integral support, the middle baffle has an upper surface, the middle baffle has a mounting groove recessed in the upper surface, the cover piece is arranged in the mounting groove, the cover piece has a support surface flush with the upper surface, the cover piece protrudes from the middle baffle in a horizontal direction, and the horizontal direction is perpendicular to the vertical direction.

5. A positioning and clamping device according to claim 4, characterized in that The integral support further comprises a second connecting plate, the sintering support further comprises a left side plate and a right side plate, the second connecting plate is fixedly connected to the integral support, the middle baffle is located above the second connecting plate, the second connecting plate is provided with an internal threaded hole, the center line of the internal threaded hole is limited to be parallel to the vertical direction, and the bolt is arranged in the internal threaded hole. The left side plate, the right side plate and the middle baffle jointly limit a mounting area for setting a coil.

6. A positioning and clamping device according to claim 5, characterized in that The middle baffle, the cover sheet, the left side plate and the right side plate are all made of brass material.

7. A positioning and clamping device according to claim 2, characterized in that A connecting rod is further included, the connecting rod is limited between the pressure head and the bolt when the piston rod is in the second state, the connecting rod is configured to be coaxial with the pressure head and the bolt respectively, one end of the connecting rod is in contact with the pressure head.

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