Information
-
Patent Grant
-
6616133
-
Patent Number
6,616,133
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Date Filed
Wednesday, July 18, 200123 years ago
-
Date Issued
Tuesday, September 9, 200320 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 092 13
- 254 93 R
- 254 93 H
- 269 32
- 269 25
- 269 27
- 269 204
- 248 3541
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International Classifications
-
Abstract
A linear actuator having an adjustable piston rod for transmitting linear motion to a rotary clamp wherein the adjustable length of the piston rod corresponds to predetermined rotational angles of a clamp arm. The adjustable piston rod provides a first portion connectable to said power clamp, and a second portion connectable to a piston of the linear actuator. The first portion is fabricated from a substantially cylindrical rod having a plurality of substantially cylindrical recesses formed thereon. The second portion provides a block connected to a tubular shaft for telescopically receiving the cylindrical rod. A cam is pivotally connected to the block and provides an aperture formed therein for receiving the cylindrical rod. A torsional spring biases the cam against the cylindrical rod within the cylindrical recesses formed in the rod to prohibit the rod from telescopically moving relative to the tubular shaft.
Description
FIELD OF THE INVENTION
The present invention relates, in general, to rotary clamps having linear actuators, and more particularly, to a rotary clamp having an adjustable piston rod that may be adjusted without the need for disassembling the rotary clamp.
BACKGROUND OF THE INVENTION
Rotary clamps are known of the type in which linear actuator reciprocating movement is adapted to be translated into rotary movement of a clamp arm. The linear actuator is typically powered by a fluid motor, and a linkage assembly is provided that converts the linear actuator movement into rotary motion of the clamp arm. The linear motion of the linear actuator is often transmitted to the linkage assembly by a piston rod. It is known to provide a threaded engagement between the end of the piston rod and the linkage assembly so that the length of the piston rod and the linkage assembly can be incrementally adjusted to a predetermined rotational angle of the clamp arm. This often requires repeated gauging and measurement of the clamp arm to ensure that the piston rod has been properly adjusted. In addition, the amount of adjustment is limited to the amount of the threaded engagement available for adjustment.
It is also known to utilize telescopic piston rods that provide the use of a pin inserted into corresponding apertures formed in the telescopic piston rod. This known design utilizes an outer shaft connected to the linear actuator and an inner shaft connected to the linkage assembly. The inner shaft is slidably received by an elongated bore in the outer shaft. A pin is removably received by one of a plurality of corresponding apertures in the outer shaft and the inner shaft of the piston rod in order to fixedly position the outer shaft to the inner shaft at a predetermined adjustable length corresponding to a predetermined rotational angle of the clamp arm. The distinct disadvantage with this known design is that the rotary clamp must be disassembled to adjust the length of the telescopic piston rod. The need to disassemble the rotary clamp increases downtime and maintenance time and reduces productivity which are all undesirable factors in an industrial environment.
It would be desirable to provide a rotary clamp that provides for the adjustment of the clamping angle of a clamp arm without having to disassemble the rotary clamp.
SUMMARY OF THE INVENTION
The present invention overcomes the above-noted shortcomings by providing an adjustable piston rod for transmitting linear motion from a linear actuator to an internal mechanism of a rotary clamp. The adjustable length of the piston rod corresponds to predetermined rotational angles of a clamp arm wherein the length of the piston rod may be adjusted without having to disassemble the rotary clamp. The adjustable piston rod of the present invention provides a hollow tubular shaft connectable to a linear actuator. A substantially cylindrical rod having a plurality of substantially cylindrical recesses formed on the outside surface of the cylindrical rod is received within the tubular shaft in a telescopic fashion. A cam is pivotally connected to the tubular shaft and provides an aperture formed therein for receiving the cylindrical rod. A torsional spring biases the cam against the cylindrical rod within the cylindrical recesses formed thereon to prohibit the cylindrical rod from moving telescopically relative to the tubular shaft.
Other options and features of the invention will become apparent by reference to the following specifications and to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, like reference numerals refer to similar elements, throughout the various views.
FIG. 1
is an exploded view of the rotary clamp utilizing the adjustable piston rod of the present invention.
FIG. 2
is a sectional view of the rotary clamp utilizing the adjustable piston rod of the present invention.
FIG. 3
is an exploded view of the adjustable piston rod of the present invention.
FIG. 4
is a sectional view showing the adjustable piston rod of the present invention in the locked position.
FIG. 5
is a sectional view showing the adjustable piston rod of the present invention in the unlocked position.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, the present invention will now be described in detail with reference to the preferred embodiment.
FIGS. 1-5
illustrate a linear actuator
14
having an adjustable piston rod
10
as defined by the present invention. As seen in
FIGS. 1-2
, the piston rod
10
is utilized within a rotary clamp
12
which is actuated by means of the linear actuator or fluid cylinder
14
. The linear actuator
14
houses a piston
13
which is attached to an end of the piston rod
10
. The fluid cylinder or linear actuator
14
is preferably pneumatic, but the fluid cylinder or linear actuator
14
may also be hydraulic. The linear actuator
14
provides linear reciprocating movement to the piston
13
which, in turn, drives the piston rod
10
in a linearly reciprocating fashion. The piston rod
10
is coupled to a linkage assembly
15
disposed within a housing
16
of the rotary clamp
12
. The linkage assembly
15
converts the linear motion of the piston rod
10
into rotary motion of a clamp arm
18
. The reciprocal linear movement of the linear actuator
14
and piston rod
10
correspond to reciprocal rotary movement of the clamp arm
18
between a clamped position and an unclamped position.
The housing
16
of the rotary clamp
12
is formed by two bilateral halves
20
wherein one end of the housing
16
is attached to the linear actuator
14
. The two halves
20
of the housing
16
form a hollow portion having a pair of laminated plates
22
disposed therein. Each of the laminated plates
22
provide an elongated guide slot
24
that is aligned with an elongated guide slot
26
formed in the inner surface of the two halves
20
of the housing
16
. The two halves
20
of the housing
16
and the pair of laminated plates
20
are connected together by fasteners
21
. The one end of the housing
16
connected to the linear actuator
14
is open to receive the free end of the piston rod
10
. The housing
16
also includes a series of coaxial apertures
28
extending through the two halves
20
and the laminated plates
22
of the housing
16
. The coaxial apertures
28
have a common axis
30
offset from and substantially perpendicular to a longitudinal axis
32
of the guide slots
24
,
26
.
To connect the adjustable piston rod
10
to the linkage assembly
15
, a rod end
38
having a U-shaped block structure threadingly engages and receives a stem-like portion of the free end of the piston rod
10
. A pin
40
extends through an aperture provided in the rounded end of the U-shaped portion of the rod end
38
. Each end of the pin
40
has substantially flat parallel landings
41
that engage the elongated guide slots
24
,
26
of the housing
16
. The pin
40
is pivotally connected to a pair of substantially parallel linkage members
42
wherein each linkage member
42
has apertures
44
for receiving the pin
40
. The apertures
44
may also be elongated (not shown) to allow for movement of the pin
40
within aperture
44
during movement of the rotary clamp
12
between the clamped and unclamped position. The linkage members
42
also provide a second aperture
47
for receiving a second pin
48
similar to pin
40
. Pin
48
is received by an aperture extending through a substantially cylindrical rubber roller
50
disposed between the linkage members
42
. The substantially flat landings of the pin
48
similarly engage the elongated slots
24
,
26
of the housing
16
as described for pin
40
.
The linkage members
42
are pivotally connected to a pair of links
54
by a pin
56
extending through corresponding apertures provided in the linkage members
42
and one end of the links
54
. At the opposite end of links
54
, the links
54
are pivotally connected to a shaft link
58
. The shaft link includes a lever arm
60
having an aperture extending therethrough. A pin
62
is inserted through aligned apertures provided in links
54
and in the lever arm
60
of the shaft link
58
.
The shaft link
58
also provides a pivot pin
68
integrally connected to the lever arm
60
. The pivot pin
68
is substantially cylindrical and is rotatably disposed within the coaxial apertures
28
provided in the housing
16
. The clamp arm
18
is connected to an exposed portion of the pivot pin
68
by fasteners
69
. The shaft link
58
also provides a positive stop
72
integrally formed in the lever arm
60
. The positive stop
72
engages a post
74
that extends between the interior walls of the housing
16
. The positive stop
72
provides an arcuate surface formed therein to complement and receive the substantially circular shape of the post
74
. The positive stop
72
abuts the post
74
to limit the travel of the clamp arm
18
in the clamped position. The rotary clamp
12
utilizes the rod end
38
, the linkage assembly
52
, and the shaft link
58
to transform reciprocal movement of the piston rod
10
into rotary movement of the clamp arm
18
between the clamped position and the unclamped position.
Even though the rotary clamp
12
is designed not to open unexpectedly upon the loss of power and/or air pressure to the linear actuator
14
, it may be desirable to move the rotary clamp
12
to the unclamped position in order to release a workpiece (not shown) or reset the linkage assembly
15
. To move the rotary clamp
12
toward the unclamped position during loss of power and/or air pressure, a reciprocal member
84
is slidably disposed within an aperture provided within an end wall of the housing
16
, as seen in FIG.
2
. The reciprocal member
84
has a cylindrical body with a pair of larger cylindrical end portions integral with the body of the reciprocal member
84
. The larger end portions capture the reciprocal member
84
within the end wall of the housing
16
. Reciprocal member
84
is aligned with the longitudinal axis
32
of the elongated slot
24
,
26
so that the reciprocal member
84
is displaced by the linkage assembly
15
when the rotary clamp
12
is in the clamped position. If power or air is lost to the rotary clamp
12
when in the clamped position, the reciprocal member
84
may be struck from the outside of the housing
16
to move the linkage assembly
15
toward the unclamped position.
To allow the linkage assembly
15
to move to an over-center position without risking wear of the internal mechanisms of the rotary clamp
10
, the present invention provides a wedging assembly that effectively wedges the linkage assembly
15
into the clamped position, as seen in
FIGS. 1 and 2
. This is accomplished by mounting two wear blocks
76
on the outside of the laminated plates
22
just above the guide slots
24
provided in the laminated plates
22
. The wear blocks
76
engage the flat landing areas provided on pins
48
,
56
when the rotary clamp
12
moves into the clamped position. Further upward pressure is applied to the pins
48
,
56
against the wear block
76
by having the roller
50
roll on an inclined surface
78
provided on the lever arm
60
of the shaft link
58
. The inclined surface
78
acts as a ramp by which the roller
50
may engage and roll thereon when the rotary clamp
10
is moving into the clamped position. By providing the inclined surface
78
on the lever arm
60
, the roller
50
provides an increasing force on pins
40
,
56
against the wear block
76
while little or no force is applied to links
54
. This assures that the clamp
18
is tightly secured when in the clamped position while also assuring that no excessive wear is occurring to the linkage assembly
15
.
In order to adjust the length of the piston rod
10
and consequently adjust the angle in which the clamp arm
18
rotates, the piston rod
10
provides an elongated member having first and second portions
90
,
86
, respectively, that are telescopically adjustable along the longitudinal axis
32
of the piston rod
10
, as best seen in
FIGS. 3-5
. The second portion
86
is fabricated from a tubular, hollow shaft having one of its ends connected to the piston
13
of the linear actuator
14
and the other of its ends threadingly received by a block or cam housing
88
. The first portion
90
of the piston rod
10
is fabricated from a substantially cylindrical solid rod that extends through the block
88
and is telescopically received within hollow shaft
86
. The opposite end of the cylindrical rod
90
is connected to rod end
38
.
To releasably lock the cylindrical rod
90
to the hollow shaft
86
, the piston rod
10
provides a cam
92
that is pivotally connected to a pivot pin or post
94
mounted within a recessed area of block
88
. The pivot pin
94
extends through an aperture
96
provided in the cam
92
wherein the cam
92
is also housed within the recessed area of the block
88
. The cam
92
provides an aperture
98
extending therethrough for receiving the cylindrical rod
90
. The aperture
98
is formed by two overlapping substantially circular apertures or arcuate portions having different radii. The larger arcuate portion
99
of aperture
98
allows the cylindrical rod
90
to freely pass through the cam
92
whereas the smaller arcuate portion
101
of aperture
98
is designed to cooperatively engage the substantially circular recesses
100
that are formed on and longitudinally spaced along the outer surface of the rod
90
.
To maintain engagement of the cam
92
with the circular recesses
100
of the rod
90
, the cam
92
is biased against the cylindrical rod
90
by a torsional spring
102
having one of its ends connected to the block
88
and another of its ends connected to cam
92
. The spring
102
is also housed within the recessed area of the block
88
. The mid-portion of the spring
102
has a coiled portion forming a substantially cylindrical, tubular shape. The coiled portion of the spring
102
receives pivot pin
94
to further support the spring
102
and to maintain the cam
92
on the pivot pin
94
as the cam
92
lies between the coiled portion of the spring
102
and a wall of the block
88
. The spring
102
biases the cam
92
so that the smaller portion
101
of aperture
98
maintains engagement with one of the cylindrical recesses
100
on the outside surface of the cylindrical rod
90
. When the smaller arcuate portion of aperture
98
is seated within a recess
100
of the cylindrical rod
90
, the rod
90
is prevented from moving telescopically relative to the hollow shaft
86
. When the cam
92
is pivoted against the bias of torsional spring
102
, the cylindrical rod
90
is disposed within the larger arcuate portion
99
of aperture
98
thus allowing rod
90
to move telescopically relative to the hollow shaft
86
.
In operation, a user (not shown) utilizes the adjustable piston rod
10
when he/she decides to change the rotational angle of the clamp arm
18
. As previously discussed, the user may adjust the rotational angle of the clamp arm
18
by adjusting the length of the piston rod
10
. As seen in
FIGS. 2-5
, access to the piston rod
10
is gained by inserting a small tool
103
into an aperture
105
provided in a wall of the housing
16
of the rotary clamp
12
when the rotary clamp
12
is in the unclamped position, that is, when the linear actuator
14
is fully retracted. When not in use, the aperture
105
may be plugged by a fastener
107
. The aperture
105
in the clamp housing
16
correspondingly aligns with an aperture
104
provided in the block
88
of the piston rod
10
when the rotary clamp
12
is in the clamped position. The aperture
104
is in communication with the recess provided in block
88
.
To engage and pivot the cam
92
against the bias of spring
102
, the tool
103
is inserted through the aperture
105
in the clamp housing
16
and through the aperture
104
in the block
88
. The tool
103
engages the cam
92
and pivots the cam
92
against spring
102
The cam
92
has a small shoulder
106
that engages a corresponding shoulder
107
provided on the inside of the block
88
to act as a positive stop in preventing the cam
92
from pivoting beyond a predetermined position. When the cam
92
is pivoted against the bias of spring
102
, the larger arcuate portion
99
of aperture
98
receives cylindrical rod
90
so that the rod
90
is free to move telescopically relative to hollow shaft
86
. This establishes the “unlocked position” of the piston rod
10
, as shown in FIG.
5
. To adjust the length of the piston rod
10
, the user simply rotates the clamp arm
18
while maintaining engagement of the cam
92
against the bias of spring
102
until the user determines the angle in which he wishes the clamp arm
18
to rotate. Upon determining the proper length of the piston rod
10
and the desired starting rotational position of the clamp arm
18
, the user removes the tool
103
and releases the cam
92
so that the portion of cam
92
that defines the smaller portion
107
of aperture
98
may engage the closest circular recess
100
on the cylindrical rod
90
. This establishes the “locked position” of the piston rod
10
, as shown in FIG.
4
. If the cam
92
is not properly aligned with one of the recesses
100
on the rod
90
, then the clamp arm
18
may be slightly rotated until the cam
92
engages one of the recesses
100
. The rotary clamp
12
is then ready to be utilized.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments, but to the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claim. The scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.
Claims
- 1. A linear actuator comprising:an elongated member having opposite ends wherein one of said opposite ends is connectable to a piston and the other of said opposite ends is connectable to a linkage assembly of a clamp, wherein said elongated member is adjustable along a longitudinal axis of said elongated member; cam means, coupled to said elongated member, for releasably locking said elongated member into a pre-determined position along said longitudinal axis; and wherein said releaseable cam means provides a cam having an aperture extending therethrough for receiving a first portion of said elongated member, and said cam movably coupled to a second portion of said elongated member between a locked position, wherein said cam cooperatively engages said first portion of said elongated member to lock said elongated member into said predetermined position, and in unlocked position, wherein said cam disengages said first portion of said elongated member to freely adjust said elongate along its longitudinal axis.
- 2. The linear actuator stated in claim 1, further comprising:a spring having one end connected to said cam and another end coupled to said second portion of said elongated member to bias said cam toward said locked position.
- 3. The linear actuator stated in claim 2 in combination with a rotary power clamp, comprising:said clamp having a housing for housing said linkage assembly and said cam, and said housing having a wall with an aperture extending therethrough for accessing and disengaging said cam from said locked position without having to disassemble said clamp.
- 4. A linear actuator comprising:an elongated member having the first and second portion wherein said first portion is connectable to a linkage assembly of a clamp, and said second portion is connectable to a piston wherein said elongated member is adjustable along a longitudinal axis of said elongated member; a cam movably connected to said second portion of said elongated member for movement between a locked position, wherein said cam cooperatively engages said first portion of said elongated member to releasably lock said elongated member into a predetermined position along said longitudinal axis, and an unlocked position, wherein said cam disengages said first portion of said elongated member to allow said elongated member to adjust along said longitudinal axis; said first and second portions of said elongated member are telescopically adjustable along said longitudinal axis; and said second portion of said elongated member having a cam housing in a shaft wherein said cam housing is connected to said shaft; a pivot pin connected to said cam housing or pivotally receiving said cam; and a spring having its ends connected to said cam housing in said cam to bias said cam towards said locked position.
- 5. The linear actuator stated in claim 4, further comprising:said cam housing having an aperture extending therethrough, and said aperture being substantially perpendicular to said longitudinal axis of said elongated member to provide access to said cam for moving said cam toward said unlocked position.
- 6. A linear actuator comprising:an elongated member having a first and second portion wherein said first portion is connected to a linkage assembly of a clamp, and said second portion is connectable to a piston wherein said elongated member is adjustable along a longitudinal axis of said elongated member, a cam movably connected to said second portion of said elongated member for movement between a locked position, wherein said cam cooperatively engages said first portion of said elongated member to releasably lock said elongated member into a predetermined position along said longitudinal axis, and an unlocked position, wherein said cam disengages said first portion of said elongated member to allow said elongated member to adjust said longitudinal axis; and said cam having an aperture extending there through for receiving said first portion of said elongated member, and said aperture formed by first arcuate portion corresponding to said locked position, and a second arcuate portion corresponding to said unlocked position, wherein said second arcuate portion is larger than said first arcuate portion.
- 7. The linear actuator stated in claim 5 in combination with a power clamp comprising:said power clamp having a clamp housing for receiving said cam housing, and said clamp housing having a wall with an aperture extending therethrough for corresponding alignment with said aperture in said cam housing to provide access to and disengage said cam without disassembling said power clamp.
- 8. A linear actuator comprising:an elongated telescopic member having a first portion connectable to a power clamp, and a second portion connectable to a piston, and said telescopic member telescopically adjustable along a longitudinal axis of said telescopic member; a cam pivotally connected to said second portion of said telescopic member for movement between a locked position, wherein said cam cooperatively engages said first portion of said telescopic member to releasably lock said telescopic member in a predetermined position, and an unlocked position, wherein said cam disengages said first portion of said telescopic member to allow said telescopic member to telescopically adjust along said longitudinal axis; a spring having one of its ends connected to said second portion of said telescopic member and the other of its ends connected to said cam to bias said cam toward said locked position; and said cam having an aperture extending therethrough for receiving said first portion of said telescopic member, and said aperture having a first arcuate portion for receiving said first portion of said first telescopic member and said locked position, and second arcuate position for receiving said first portion of said telescopic member in said unlocked position, wherein said first arcuate portion is smaller than said second arcuate portion.
- 9. A linear actuator comprising:an elongated telescopic member having a first portion connectable to a power clamp, and a second portion connectable to a piston, and said telescopic member telescopically adjustable along a longitudinal axis of said telescopic member; a cam pivotally connected to said second portion of said telescopic member for movement between a locked position, wherein said cam cooperatively engages said first portion of said telescopic member to releasably lock said telescopic member in a predetermined position, and an unlocked position, wherein said cam disengages said first portion of said telescopic member to allow said telescopic member to telescopically adjust along said longitudinal axis; a spring having one of its ends connected to said second portion of said telescopic member and the other of its ends connected to said cam to bias said cam towards said locked position; and said second portion of said telescopic member having a cam housing and a shaft wherein said cam housing has a threaded aperture extending therethrough for threadingly receiving said shaft; and said cam housing having a sidewall with an aperture extending therethrough at an angle substantially perpendicular to said longitudinal axis to provide access to said cam for movement of said cam towards said unlocked position.
- 10. A linear actuator comprising:an elongated member having opposite ends wherein one of said opposite ends is connectable to a piston and the other of said opposite ends is connectable to a linkage assembly of a clamp, wherein said elongated member is adjustable along a longitudinal axis of said elongated member; and a cam having an aperture extending threrethrough for receiving said elongated member and for releasably locking said elongated member into a predetermined position along said longitudinal axis.
US Referenced Citations (16)