JPH0233883B2 - - Google Patents

Abstract

A piston (16) and rod (18) slide in a double acting cylinder with closed end (12) from which extends a bar (60) having a T-shaped cross-section with a cross piece (64) and stiffening web (66), the edges of which are rounded to engage and slide on the wall of a bore (22) in the piston rod (18), thus supporting the bar in a rigid manner. The face (68) of the cross piece (64) supports a potentiometer track which co-operates with a wiper (118) carried by an insulating carrier (110) fitted into the bore (22). The T-shaped bar (60) partitions the bore (22) into three chambers (65, 67, 69) which are in communication at the distal end of the bar. The carrier (110) is shaped to close the chamber (65) containing the wiper so that there is no fluid flow past the wiper as the piston (16) moves.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a position sensor (transducer) with a potentiometer.

In hydraulic control technology, it is sometimes desirable to obtain a feedback signal representative of the operating position of a hydraulic cylinder. US Pat. No. 3,726,191 provides one solution to this problem. In the hydraulic cylinder according to this U.S. patent, a hole extending in the axial direction is provided in a piston rod that relatively reciprocates within the housing of the cylinder, and
A potentiometer assembly including a rod-shaped resistive conductor element support fixed to the housing and extending into the bore and having a resistive conductor element, the wiper disposed in the bore engaging the resistive conductor element. It is equipped with However, the resistive conductor element set in the bore of this piston rod, as well as its support, has a large cross-sectional area and therefore, when the piston rod moves relative to the cylinder housing, a relatively large amount of force is applied to the bore. Fluid flows in and out. Therefore, the wiper set in the hole is likely to vibrate due to the flow of fluid and cause noise in the measurement signal during operation of the potentiometer.

It is an object of the present invention to provide a position sensing hydraulic cylinder that solves these problems.

Namely, the position-sensitive hydraulic cylinder according to the present invention comprises: a hollow cylindrical housing (indicated by the reference numeral 12 in the embodiments described below); a piston rod assembly 16, 18 slidable within the housing; a bore 22 extending axially within the piston rod assembly; a coaxially extending flat support surface fixed to the housing and configured to extend within the bore inserted into the bore; Support 6 with 68
0; a potentiometer having a potentiometer element 76 disposed on said support surface and a conductive wiper means 118 slidably and resiliently engaged with said element to maintain electrical connection; an assembly 72; a wiper carrier 118 adapted to move with the piston rod assembly to move the wiper means relative to the potentiometer element;
and; the wiper carrier cooperates with the support and the wall of the aperture to substantially prevent fluid flow proximate the wiper means, and the potentiometer assembly is coupled to the wiper means and the potentiometer element. The feature is that a signal representing the relative position between the two is generated.

As can be seen from the above, in the position-sensitive hydraulic cylinder according to the invention, the wiper carrier supporting the wiper has a support that extends into the bore of the piston rod and supports the potentiometer element, together with the wall of the bore. Since the structure is configured to substantially block the flow of fluid near the wiper means, the wiper means will not vibrate due to the flow of fluid even when the piston rod moves relative to the cylinder housing. Therefore, the above-mentioned problems of the conventional position sensing hydraulic cylinder can be solved.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

As shown, a hydraulic cylinder 10 according to the present invention
has a housing 12 having a hollow cylindrical portion 14 within which the rod 1 is disposed.
A piston 16 connected to the piston 8 is provided so as to be able to reciprocate. A rod receiving cap 20 is threadedly engaged to one end of the housing 12. A stepped bore 22 extends within the piston 16 and rod 18.

As best shown in FIG. 2, the stepped bore 22 has a large diameter portion 24, a small diameter portion 30, and an annular shoulder 32 extending therebetween, with the large diameter portion 24 forming a snap spring groove. 26 and an annular raised portion 28.

Housing 12 has a threaded hole 34 for threadedly engaging an external transducer member 36 made of steel.
The member 36 has an annular flange 38 adapted to abut a corresponding housing shoulder 40. An O-ring 42 seals between transducer member 36 and housing 12. The transducer member also has a stepped hole 44 extending therethrough.
have.

A steel terminal member 46 is press fit into the hole 44. Terminal member 46 has an annular groove 48 for receiving support ring 50 and O-ring 52 to provide a seal between transducer member 36 and terminal member 46 .
A ceramic member 54 is provided in the hollow interior of the terminal member 46.
is installed and the inside is sealed. Terminal member 4
6 is made separately from the transducer member 36, and when the ceramic member is heated within the terminal member,
Transducer member 36 is prevented from degrading by the high temperatures it would be exposed to if it were integrally molded with the terminal member.

A steel transducer support 60 extends into the bore 22 from one end 62 received and welded to the terminal member 46. One end 62 of support 60 is rigidly supported relative to housing 12 by members 36 and 46. This is true in conventional position sensing cylinders, such as those disclosed in U.S. Pat. No. 3,726,191.
In contrast to those in which the transducer support is press-fitted into a plastic insulating sleeve received by a metal threaded fitting, the support can be rigidly supported. Further, in the present invention, the ceramic sealing member 54 is attached to the support body 60.
It is hardly affected by mechanical forces such as vibrations. Ceramic sealing member 54 only needs to withstand hydraulic pressure, thus providing an excellent hydraulic pressure seal in the cylinder according to the invention.

As shown in FIGS. 3 and 4, the support 60 includes a transverse section 64 and a stiffened section 6 extending perpendicularly therefrom.
It has a T-shaped cross section consisting of 6. The transverse section 64 has a flat support surface 68. As shown in FIGS. 2 and 4, a circular edge notch 70 is formed in the end 62 of the support 60. As shown in FIGS.

A transverse section 64 and a stiffened section 66 divide the bore 22 into three chambers 65, 67, 69. As best shown in FIGS. 2 and 3, the curved outer circumferential surfaces 59, 61, 63 of support 60 slidably engage the inner wall of hole 22. As best shown in FIGS. This engagement causes the support 6
0 is prevented from bending and vibrations are reduced. These bending and vibrations would be experienced if the support were supported at only one end and cantilevered.

As best shown in FIGS. 5 and 6a-6b, a resistor or potentiometer assembly 72 is mounted on the flat support surface 68 of the transverse portion 64 of the support 60. Assembly 72 has an electrically insulated base 74 attached to support surface 68 . The base is made from a material such as that sold under the trademark "Kapton" by DuPont.

Assembly 72 also includes a conductive plastic potentiometer element 76. The longest central portion of the potentiometer rests directly on the base 74. Ends 78, 8 of the potentiometer element
0 is superimposed on a metal conductive ground member 82 and a power strip 84. Potentiometer element 76
end at edges 79,81. A grounding member 82 is connected to the lower edge 8 of the end 78 of the potentiometer element 76.
3 (Figure 5). A conductive wire 86 is connected to the outer end of the grounding member 82. power strip 8
4 terminates at the lower edge 85 of the end 80 of the potentiometer element 76. These conductive members 82,
The overlap between 84 and the ends 78, 80 of the potentiometer element is sufficient to form a good electrical connection. The outer end of power strip 84 is connected to conductor 88.
connected to. A conductive connection strip 90 is also positioned on the insulating base 74. Strip 90 extends from edge 92 to end 94, which end is connected to conductor 96. An overlapping strip 98 of conductive plastic material is provided over conductive strip 90 and extends from edge 99 to edge 9.
It extends to 2. It should be noted that the potentiometer assembly 72 is not received within a recess or groove in the support 60, but is positioned on the flat support surface 68 of the support 60. The absence of recesses or grooves in the support reduces the possibility of metal powder creating an undesirable short circuit between the outer edges of power strip 84 and connection strip 90 and support 60.
For clarity, the various strip thicknesses in Figures 6a-6d are shown enlarged.

Conductive wires 86, 88, and 96 extend through notch 70, terminal member 46, and ceramic seal member 54 to connection terminals 100, 102, and 104, respectively.
The connection terminals 100, 102, 104 are connected to ordinary female plug type connectors.

As best shown in FIG. 2, a wiper carrier 110 is provided within portion 24 of bore 22. As best seen in FIG.
The wiper carrier 110 has a generally cylindrical section 112 of insulating material, such as tempered glass nylon, with an annular recess 114 at one end thereof. The tongue and groove 114 mate with the annular ridge 28 only when the wiper carrier is properly seated within the hole portion 24, and otherwise align with the annular ridge 28.
The wiper carrier 110 enters the hole portion 24,
Prevents the snap ring 126 from entering the snap ring groove 26. Wiper support flange 1
16 extends inwardly from a portion of cylindrical portion 112 . A fork-shaped conductive wiper 118 is supported on the flange 116 and includes fork portions 120,1.
22 resiliently engages a plastic conductive stop 98 on connection strip 90 and a surface of potentiometer element 76, respectively. Wiper 11
8 extends into chamber 65. As best shown in FIG. 7, fork portions 120, 122 have a plurality of fingers. Rectangular recess 124
is formed in an inner surface 125 of carrier flange 116 such that inner surface 125 is aligned with surface 68 of support 60 and transducer element 72 . The carrier 110 is located between the snap spring 126 and the resilient wave washer 128 and is adapted to move with the rod 18 and piston 16.

The piston 16 and the rod 18 are connected to the housing 12.
and when moving back and forth relative to support 60, fluid enters and exits chamber 65 around end 129 of support 60 and through chambers 67, 69. However, the inner surface 125 of the carrier flange 116, the support surface 68 and the potentiometer assembly 72
The tight sliding engagement between substantially prevents flow through the wiper carrier 110 into and out of the chamber 65, thus reducing turbulence in the liquid near the wiper 118. This reduction in turbulence is due to wiper 1
18 and prevents the generation of noise in the signal picked up by the wiper 118.

In operation, a voltage is applied between terminals 102 and 100, thereby creating a corresponding potential difference across potentiometer element (resistive element) 76. The piston 16 and the rod 18 are connected to the housing 1
2, wiper 118 moves with piston 16 and piston rod 18 relative to support 60 and transducer element 72. Thus, the voltage across the wiper 118 varies from ground voltage to approximately the voltage at the power strip, depending on the relative longitudinal position of the wiper 118 to the resistive element 76. Wiper 118 voltage is connected to connection strip 98,
90 is connected to the exterior of the cylinder housing 12 through a conductor 96 and a terminal 104 so that a signal indicating the position of the cylinder 10 can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a hydraulic cylinder according to the present invention; FIG. 2 is a partial sectional view of the cylinder; FIG. 3 is a 3-3 line diagram in FIG. 2; 4 in figure 2
-4 line diagram; Figure 5 is a plan view of the terminal member and converter support; Figures 6a to 6d are A-A, BB, CC, and D-D of Figure 5, respectively; A line sectional view; FIG. 7 is an end view of the wiper carrier. 12... Housing; 16... Piston; 18
... Rod; 60 ... Support; 72 ... Potentiometer assembly; 78 ... Potentiometer element; 11
0...Waipa carrier; 118...Waipa.

Claims (1)

[Scope of Claims] 1. A hollow cylindrical housing; a piston rod assembly slidable within the housing; a hole extending in the axial direction of the piston rod assembly; fixed to the housing; a support configured to be inserted into and extend axially within the hole, the support having a coaxially extending flat support surface; a potentiometer element provided on the support surface; a potentiometer assembly having a conductive wiper means slidably and resiliently engaged to maintain electrical connection; a piston for moving the wiper means relative to the potentiometer element; a wiper carrier adapted to move with the rod assembly; the wiper carrier cooperating with the support and the wall of the aperture to substantially prevent fluid flow proximate the wiper means; A position sensitive hydraulic cylinder, wherein the potentiometer assembly generates a signal representative of the relative position between the wiper means and the potentiometer element. 2. The support has a transverse portion forming a flat support surface, and a hardened portion extending perpendicularly from the transverse portion;
2. A position-sensitive hydraulic cylinder according to claim 1, having a substantially T-shaped cross-section formed by the transverse portion and the stiffened portion. 3. A transverse section and a stiffening section divide the hole into first, second and third chambers, a transverse section separating the first chamber from the second and third chambers, and a stiffening section separating the first chamber from the second and third chambers.
and a third chamber, the second and third chambers being open at opposite ends thereof to allow fluid to flow through the second and third chambers upon relative movement of the piston and the housing, and the wiper The means is within the fluid within the first chamber, and the wiper carrier cooperates with the wall and transverse portion of the first chamber.
3. A position sensitive hydraulic cylinder as claimed in claim 2, wherein one end of the chamber is closed to thereby substantially prevent fluid flow near the wiper means. 4. A patent in which the transverse portion and the hardened portion have a curved surface that slides into engagement with the wall 9, and the engagement between the surface and the wall of the hole provides resistance to deformation of the support. A position sensitive hydraulic cylinder according to claim 2. 5 The wiper carrier has a cylindrical member having a concave portion at one end of the outer circumferential surface, and the hole is a stepped hole having a large diameter portion and a small diameter portion connected by an annular shoulder, and the large diameter a portion for receiving the wiper carrier and having an annular ridge at one end aligned with the recess in the wiper carrier, the annular shoulder for limiting relative movement between the wiper carrier and the rod; A position-sensitive hydraulic cylinder as claimed in claim 1 forming an abutment. 6. a hollow member sealingly and removably attached to one end of the housing; a hollow sleeve received and sealingly connected to the hollow member and having means for firmly supporting one end of the support; a sealing plug member formed within the hollow sleeve and adapted to prevent flow through the hollow sleeve at a location spaced from the support; Cylinder.