JPH031661Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a rod seal that is disposed between a piston rod and a cylinder head penetrated by the piston rod to seal pressure fluid.

(Prior Art) As a rod seal disposed between a piston and a cylinder head to seal pressure fluid, the one illustrated in FIG. 2 is widely used.

The rod seal shown in the figure includes substantially cylindrical bearings 3 arranged on the inner circumferential side of a cylinder head 2 penetrated by a piston rod 1, and a seal lip 5 on the inner circumferential side with a substantially U-shaped cross section. It has a packing 4 and a dust seal 6 having a substantially truncated shape, and guides the reciprocating movement of the piston rod 1 by a bearing 3, and the pressure fluid flows out by elastic contact of the seal lip 5 of the packing 4 with the circumferential surface of the piston rod 1. The elastic contact of the dust seal 6 with the circumferential surface of the piston rod 1 prevents external dust from entering.

(Problems to be Solved by the Invention) In the rod seal according to the prior art described above, when the eccentricity of the piston rod 1 with respect to the cylinder head 2 becomes large or when the piston rod is operated in a low temperature environment, the rubber-like elastic material packing 4 undergoes low-temperature shrinkage. If this occurs, there remains a risk that the contact between the bottom peripheral surface of the mounting groove of the cylinder head 2 and the packing 4 may become unstable, resulting in a decrease in sealing performance.

The above-mentioned eccentricity of the piston rod 1 with respect to the cylinder head 2 tends to occur when there is not enough room to install the bearing 3, and it tends to become more pronounced as the working pressure increases as seen in the recent trend. Since this tendency tends to increase as the usage environment becomes lower in temperature, the risk of the above-mentioned deterioration of the sealing function is significantly increasing.

The object of the present invention is to solve the above-mentioned problems and to provide a rod seal structure that prevents deterioration of the sealing function due to eccentricity between the piston rod and cylinder head and low-temperature shrinkage of the packing.

(Means for Solving the Problems) In view of the problems with the rod seals according to the prior art described above, the present invention is based on a packing made of an elastic material and having a seal lip that seals and slides on the circumferential surface of the piston rod. A tightening margin is set between the heel part and the bottom peripheral surface of the mounting groove provided in the cylinder head, and an annular recess is provided inside the heel part, and the inner peripheral side is made into a conical surface using a hard material. The formed back-up spring is press-fitted into the annular recess of the heel part, and a support ring made of a slightly soft synthetic resin material and whose outer circumferential surface is a conical surface equivalent to the inner circumferential surface of the back-up spring is inserted. It is arranged between the back up spring and the seal lip of the packing.

(Function) In the rod seal having the above configuration, the back-up spring is made of a hard material and press-fitted into the annular recess provided inside the heel of the seal. The heel of the packing is sandwiched between the bottom peripheral surface of the mounting groove of the cylinder head, and the outer peripheral surface is formed into a conical surface equivalent to the inner peripheral surface of the back-up spring using a slightly soft synthetic resin material. When the support ring placed between the seal lip of the seal and the back-up spring is compressed by the fluid pressure, it is pushed by the conical surface of the back-up spring and contracts, bringing its inner circumferential surface into contact with the circumferential surface of the piston rod. When the piston rod becomes eccentric, the part of the support ring located at the point where the distance between the piston rod and the back up spring becomes narrower will move to the side where the distance between the two members becomes wider. The state of support for the entire circumferential surface of the piston rod is maintained.

(Embodiment) In the embodiment shown in FIG.
An outward protrusion 8 is attached to the outer periphery of the heel portion 7 of the packing 4, which has a seal lip 5 that seals and slides on the circumferential surface of the sealer head 2, and a tightening margin is set between the heel portion 7 and the bottom circumferential surface of the mounting groove of the sealer head 2. A back-up spring 1 made of a metal material and having an inner circumferential surface formed into a conical surface is installed in an annular recess 9 provided inside the heel portion 7.
0 is inserted to sandwich the heel portion 7 between the heel portion 7 and the bottom peripheral surface of the mounting groove, and a support ring 11 made of a synthetic resin material whose outer peripheral surface is formed into a conical surface equivalent to the inner peripheral surface of the back-up spring 10. It is arranged between the backup spring 10 and the seal lip portion 5.

In the embodiment described above, when the packing 4 contracts due to low temperature, the tightening margin of the outward protrusion 8 against the bottom peripheral surface of the mounting groove and the back-up spring 10 are reduced.
This supporting force prevents the formation of a gap between the heel portion 7 and the bottom peripheral surface of the mounting groove due to contraction of the packing 4, and when eccentricity of the piston rod 1 with respect to the cylinder head 2 occurs, the back-up spring 10 and The portion of the support ring 11 at the location where the gap between the circumferential surfaces of the piston rod 1 is narrowed is pushed out by the narrow pressure in the direction where the gap between the two members is widened, thereby maintaining the state of support for the entire circumferential surface of the piston rod 1.

(Effect of the invention) As mentioned above, the rod seal of the invention has
A tightening margin is set between the heel of the packing having a seal lip that seals and slides against the circumferential surface of the piston rod and the bottom circumferential surface of the mounting groove of the cylinder head,
A back-up spring made of a hard material with an inner circumferential surface formed into a conical surface is inserted into an annular recess provided inside the heel part, and an outer circumferential surface is further formed into an equivalent conical surface on the inner circumferential surface of the back-up spring. By having a structure in which the support ring is placed between the back up spring and the seal lip of the packing using a slightly soft material, it is possible to prevent the packing from shrinking at low temperatures and eccentricity of the piston rod relative to the cylinder head. The formation of a gap between the bottom peripheral surface of the mounting groove and the heel part is prevented by the interference of the heel part with respect to the bottom peripheral surface of the mounting groove and the supporting force of the back-up spring against the heel part, and the eccentricity of the piston rod with respect to the cylinder head is prevented. The formation of a curved gap between the circumferential surface of the piston rod and the support ring at the time of occurrence causes the part of the back-up spring where the gap between the piston rod and the back-up ring to become narrow to be pushed out by the narrow pressure, and both members This is prevented by moving the piston rod toward a wider gap and maintaining support for the entire circumferential surface of the piston rod, so the sealing performance of the packing is good even at low temperatures or when the piston rod is eccentric with respect to the cylinder head. The pressure device can continue to function normally for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of an example of a rod seal according to the prior art. 1... Piston rod, 2... Cylinder head, 3... Bearing, 4... Packing, 5... Seal lip, 6... Dust seal, 7... Heel part,
8... Outward projection, 9... Annular recess, 10... Backup spring, 11... Support ring.

Claims (1)

[Scope of utility model registration request] A heel portion 7 of an elastic packing 4 having a seal lip 5 that seals and slides against the circumferential surface of the piston rod 1 that reciprocates through the cylinder head 2, and a bottom circumferential surface of a mounting groove provided in the cylinder head 2. In addition to setting a tightening margin between
A back-up spring 10 is provided with an annular recess 9 inside the heel portion 7 and has a conical inner circumferential surface.
is inserted into the recess 9, and a support ring 11 made of a synthetic resin material and having an outer circumferential surface formed into a conical surface equivalent to the inner circumferential surface of the back-up spring 10 is attached to the back-up ring 10 and the seal lip 5.
A rod seal characterized by being placed between the two.