WE CLAIM:
Claim 1. A fluid pressure device comprising:
a body having a slide hole (13, 103) inside the body;
5 a piston unit (18, 18a to 18g) movable in an axial
direction inside the slide hole (13, 103); and
a piston rod (20, 71, 72, 75, 78, 108) protruding from
the piston unit (18, 18a to 18g) in the axial direction;
wherein:
10 the piston unit (18a to 18g) includes a packing (34,
82) and a piston body (38) comprising a plurality of
members, the piston body being provided with a packing
mounting groove (36, 85) in which the packing (34, 82) is
mounted;
15 the piston body (38) includes, as the plurality of
members, a first piston member (40, 69, 73, 77, 79) and a second piston member (42, 70, 80) stacked in the axial direction;
a combination of at least two members of the plurality 20 of members defines the packing mounting groove (36, 85); and one or both of the first piston member (40, 69, 73, 77, 79) and the second piston member (42, 70, 80) are provided with a lightening portion (46) having a depth in the axial direction. 25
Claim 2. The fluid pressure device according to claim 1, wherein the first piston member (40, 69, 73, 77, 79) and the second piston member (42, 70, 80) are castings.
30 Claim 3. The fluid pressure device according to claim
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1, wherein the lightening portion (46) has a through-hole (47) passing through only one of the first piston member (40, 69, 73) and the second piston member (42, 70) in the axial direction. 5
Claim 4. The fluid pressure device according to claim
3, wherein:
one member of the first piston member (40, 69, 73) and the second piston member (42, 70) that is provided with the 10 through-hole (47) includes a protruding portion (50)
protruding toward another member of the first piston member (40, 69, 73) and the second piston member (42, 70) that is not provided with the through-hole (47); and
the protruding portion (50) has, on an outer 15 circumferential part thereof, a recess portion (51) recessed inward and which constitutes part of the through-hole (47).
Claim 5. The fluid pressure device according to claim
4, wherein:
20 the piston body (38) further includes a magnet (48) or
a spacer (76, 76a) as the plurality of members; and
the protruding portion (50) has a supporting protrusion (52) protruding outward on the outer circumferential part and at a circumferential position different from a position
25 of the recess portion (51), the supporting protrusion being configured to support the magnet (48) or the spacer (76, 76a) .
Claim 6. The fluid pressure device according to claim 30 4, wherein:
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the one member provided with the through-hole (47) is provided with a wall portion (53) protruding outwardly toward the through-hole (47); and
the wall portion (53) is disposed at a position 5 adjoining the recess portion (51) on a side remote, in the
axial direction, from the other member not provided with the through-hole (47).
Claim 7. The fluid pressure device according to claim 10 6, wherein the recess portion (51) is provided with a rib (51a) configured to reinforce the wall portion (53).
Claim 8. The fluid pressure device according to claim
1, wherein:
15 the lightening portion (46) includes a first lightening
portion (46a) defined in the first piston member (40, 69, 73, 77, 79) and a second lightening portion (46b) defined in the second piston member (42, 70, 80);
one of the first lightening portion (46a) and the 20 second lightening portion (46b) is a through-hole (47)
passing through the corresponding piston member in the axial direction; and
another of the first lightening portion (46a) and the second lightening portion (46b) is a bottomed groove (54) 25 having a depth in the axial direction.
Claim 9. The fluid pressure device according to claim 8, wherein:
the through-hole (47) comprises a plurality of through-30 holes (47) disposed at intervals in a circumferential
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direction; and
the groove (54) comprises a plurality of grooves (54) disposed at intervals in the circumferential direction.
5 Claim 10. The fluid pressure device according to claim
9, wherein:
one member of the first piston member (40, 69, 73, 77, 79) and the second piston member (42, 70, 80) that is provided with the plurality of through-holes (47) includes a
10 protruding portion (50) protruding toward another member of the first piston member (40, 69, 73, 77, 79) and the second piston member (42, 70, 80) that is provided With the plurality of grooves (54);
the protruding portion (50) has a plurality of
15 supporting protrusions (52) arranged at intervals in the
circumferential direction on an outer circumferential part of the protruding portion (50), the supporting protrusions protruding outward; and
the other member of the first piston member (40, 69,
20 73, 77, 79) and the second piston member (42, 70, 80) that is provided with the plurality of grooves (54) has an abutting surface (55) disposed between two of the grooves (54) that are circumferentially adjacent to each other, the abutting surface being configured to abut against an end
25 surface of at least one of the plurality of supporting protrusions (52).
Claim 11. The fluid pressure device according to claim
10, wherein:
30 the plurality of supporting protrusions (52) include a
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first supporting protrusion (52a) abutting against the
abutting surface (55) and a second supporting protrusion
(52b) disposed at a circumferential position different from
a position of the abutting surface (55); and
5 a circumferential width of the second supporting
protrusion (52b) is smaller than a circumferential width of the first supporting protrusion (52a).
Claim 12. The fluid pressure device according to claim 10 10, wherein:
one of the first piston member (40, 69, 73, 77, 79) and
the second piston member (42, 70, 80) is provided with a
positioning protrusion (56) protruding in the axial
direction;
15 another of the first piston member (40, 69, 73, 77, 79)
and the second piston member (42, 70, 80) is provided with a positioning recess (57) recessed in the axial direction; and
the positioning protrusion (56) is inserted into the positioning recess (57).
20
Claim 13. The fluid pressure device according to claim 1, wherein the lightening portion (46) comprises a plurality of lightening portions (46) disposed at intervals in a circumferential direction.
25
Claim 14. The fluid pressure device according to claim 1, wherein the fluid pressure device is configured as a fluid pressure cylinder (10A to 10F), a valve device, a length-measurement cylinder, a sliding table, or a chuck
30 device.
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Claim 15. A method for producing a piston assembly (74a to 74e) provided with a piston unit (18, 18a to 18g) including a packing (34, 82) mounted in a packing mounting 5 groove (36, 85) and a piston rod (20, 71, 72, 75, 78, 108)
protruding from the piston unit (18, 18a to 18g), comprising the steps of:
stacking a plurality of members including a first piston member (40, 69, 73, 77, 79) and a second piston 10 member (42, 70, 80) by relatively moving the packing (34, 82) and the plurality of members in an axial direction in sequence, relative to the piston rod (20, 71, 72, 75, 78, 108); and
securing the first piston member (40, 69, 73, 77, 79) 15 and the second piston member (42, 70, 80) to the piston rod (20, 71, 72, 75, 78, 108); wherein:
the plurality of members constitute a piston body (38) provided with the packing mounting groove (36, 85);
a combination of at least two members of the plurality 20 of members defines the packing mounting groove (36, 85); and
one or both of the first piston member (40, 69, 73, 77, 79) and the second piston member (42, 70, 80) are provided with a lightening portion (46) having a depth in the axial direction.
25
Claim 16. The method for producing the piston assembly (74a to 74e) according to claim 15, wherein the piston rod (20, 71, 72, 75, 78, 108) is in an upright position during the step of stacking the plurality of members.
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