EP0937538B1

EP0937538B1 - Low profile pneumatic retractor clamp

Info

Publication number: EP0937538B1
Application number: EP19980301256
Authority: EP
Inventors: Henry Dykstra
Original assignee: Delaware Capital Formation Inc; Capital Formation Inc
Current assignee: Delaware Capital Formation Inc
Priority date: 1998-02-18
Filing date: 1998-02-18
Publication date: 2003-06-18
Anticipated expiration: 2018-02-18
Also published as: EP0937538A1; DE69815653T2; DE69815653D1

Description

The invention broadly relates to pneumatic clamps, and more particularly, to a low profile clamp which provides a clamping force in two perpendicular directions through the motion of a pneumatic cylinder in a single plane.
Power clamps are frequently used in a wide variety of work stations to forcibly clamp a workpiece in place during any conceivable number of operations necessary for the particular workpiece. A typical clamp includes clamp arms having a range of motion extending substantially outside the perimeter of the clamp body. As a result, the typical clamp requires substantial space to accommodate the motion of the clamp arms during the clamping and releasing of the workpiece. However, work space is routinely limited preventing the use of such typical clamps. Furthermore, even if work space is adequate to accommodate the range of the motion of the typical clamp, the motion may so severely interfere with other operations on the workpiece, necessary before or during the clamping function, that the clamp is rendered inoperable.
US-A-4 494 739 discloses a clamping assembly operated by a piston and cylinder assembly rotatably mounted on a support. A mounting bracket rotatably mounted on the support is provided with a pair of pivotally mounted plates each having a clamping arm and a cam track. A drive rod connected to the piston extends through the support and into an elongate slot in the bracket. Rollers secured to the outer end of the rod are disposed in the cam slots and drive the plates to pivot. The cam slots are configured to lock the clamp in a locking position in the event that fluid pressure is lost in the piston.
EP-A-0 213 400 discloses a chucking fixture for work pieces comprising a clamping finger supported for swivelling and for moving longitudinally and a pressure-operated piston controlling the clamping finger responsive to the piston travel so that the swivel and displacement movements are performed successively. The piston has an oblique control surface on which a sliding element of the clamping finger is slidable to swivel the clamping finger transverse to the piston direction. A stop is provided at the piston which, at the end of the sliding movement, entrains the clamping finger in the direction of the piston. The piston is arranged transverse to the clamping finger. The sliding element engages a stop of the housing to keep the clamping finger in axial alignment as long as the clamping finger has not reached its outermost position. The sliding element leaves the stop attached to the casing only in the outermost position of the clamping finger to allow for swivel movement of the clamping finger.
DE-A-1 478 857 discloses a clamp which uses a large spring to hold a clamp arm in a predefined position.
According to the present invention there is provided a low profile clamp comprising:
a clamp body having a longitudinal bore;
a cylinder having a fluid chamber therein and removably attached to said clamp body along the longitudinal axis, said cylinder including a pair of fluid ports longitudinally spaced from one another in fluid communication with said fluid chamber;
a bracket slidingly held within the bore of said clamp body;
a piston rod longitudinally disposed in said bore and having a first end removably secured to said bracket;
a piston removably attached to the piston rod opposite the first end, said piston being sealingly disposed for slidable, longitudinal movement within said fluid chamber between said fluid ports in order to selectively extend and retract said piston rod longitudinally in response to respective greater and lesser fluid pressures in one of said fluid ports with respect to the other of said fluid ports; and
a clamp block slidingly held within the bore of said clamp body, said clamp block having a first end held within the bracket and slidingly cooperating along an angled path relative to the longitudinal motion of the bracket, said clamp block further including a clamp arm extending from a second end and a portion protruding outside the clamp body.
The hereinafter described and illustrated preferred embodiments of low profile clamp minimise the range of motion for the clamp arms while providing sufficient clamping power. They also have a low profile to maximise accessibility to a workpiece.
Embodiments of apparatus in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings, described below.
FIG. 1 is a perspective view of a low profile clamp according to the present invention.
FIG. 2 is an exploded view of the present invention excluding the clamp body.
FIG. 3 is a longitudinal cross-sectional view of the present invention in a retracted position.
FIG. 4 is a longitudinal cross-sectional view of the present invention in an extended condition.
FIG. 5 is a longitudinal side view of the clamp block for the present invention.
FIG. 6 is a right end view of figure 5.
FIG. 7 is a bottom view of figure 5.
FIG. 8 is a left end view of figure 5.
FIG. 9 is a view of the pivot for the present invention.
FIG. 10 is a longitudinal view of figure 9 rotated 90°.
FIG. 11 is a side view of figure 9.
FIG. 12 is a longitudinal side view of the body for the present invention.
FIG. 13 is a top view of figure 12.
FIG. 14 is longitudinal cross-sectional view of figure 12.
FIG. 15 is a right end view of figure 12.
FIG. 16 is a transverse cross-sectional view taken along line A-A of figure 12.
FIG. 17 is a longitudinal side view of the pneumatic cylinder with a partial cross-sectional view.
FIG. 18 is a fragmentary side view of figure 17.
FIG. 19 is a longitudinal side view of the clevis bracket for the present invention.
FIG. 20 is a bottom view of figure 19.
FIG. 21 is a right end view of figure 19.
FIG. 22 is a left end view of figure 19.
FIG. 23 is a fragmentary view of figure 19 more particularly illustrating the slot.
FIG. 24 is a fragmentary pictorial view of a second embodiment of the present invention illustrating a clamp adaptor.
FIG. 25 is a top view of the clamp adaptor of figure 24 secured to the clamp arm of the present invention.
Referring now in greater detail to the drawings, figure 1 demonstrates the present invention is a low profile pneumatic clamp 10 which provides a clamping force in two perpendicular directions through the motion of a pneumatic cylinder in a single plane. The principle component of the clamping force is a horizonal force in line with the force generated by the pneumatic air cylinder. An additional vertically downward clamping force is also generated.
The fixture clamp 10, shown in Fig. 1 and Fig. 2, generally comprises an air cylinder 20 and a clamp body 30 containing a clevis bracket 40, a clamp block 50 and a pivot piece 60. The air cylinder 20 is attached to the clamp body 30 within which the clevis bracket 40 and clamp block 50 are slidingly held. The driven portion of the air cylinder 20 is threadingly attached to the clevis bracket 40 and both are movable along the axis of the air cylinder 20 within the clamp body 30. The clamp block 50 is held relative to the clevis bracket 40 by pin member 42 within slots 44 in the arms 46 of the clevis bracket 40. A tension spring 55 is securely positioned between the clevis bracket 40 and clamp block 50 within aligned recesses 47, 57, respectively, to bias each apart. At the end of the clamp block 50 is the clamp arm 52 which has a suitable configuration for clamping the particular work piece, here more particularly shown in figures 5-8, with a simple rectangular configuration for holding the square edge of a typical work piece.
It is understood that a simple clamping pin (not shown) could be used which could be inserted into any number of clamping heads (not shown) which could have a variety of configurations depending on the work piece, including a roughened surface for frictional grip, or resilient surfaces for preserving a finish on a work piece or for softer work pieces. Additionally, it is understood that the clamp could be powered by any fluid actuating means, including pneumatically or hydraulically powered systems.
As shown in figure 3, the clamp arm 52 is slightly angled upwardly of the axis of the motion of the pneumatic cylinder 20, clevis bracket 40 and clamp block 50 when the piston 22 and piston rod 23 are in the retracted position. The clamp arm 52 is slidingly held within a pivot piece 60, more particularly illustrated in figures 9-11, which is rotatably held within the clamp body 30 at the end opposite the pneumatic cylinder 20. As the piston 22 and piston rod 23 move the clevis bracket 40, the clamp block 50 is moved axially within the clamping body 30 once the compressive force of the spring 55 is overcome, causing the clamp arm 52 to advance through the pivot piece 60.
When the vertical clamping surface 58 of the clamp arm 52 (which provides the horizontal clamping force) engages the work piece (not shown), the axial motion of the clamp block 50 is halted. The piston 22 and piston rod 23 continue to advance, advancing the clevis bracket 40 which overcomes the biasing force of the spring 55 and continues to move the clevis bracket 40 relative to the clamp block 50 forcing the pin 42 to ride up through the slots 44 in the arms 46 of the clevis bracket 40. This forces the end of the clamp block 50 upward and to pivot about the pivot piece 60 which causes the end of the clamp arm 52 to pivot vertically downward. The spring 55 is sufficiently resilient to deform under these conditions and the piston 22 and piston rod 23 are adjusted to advance until the pin 42 has traveled to the end of the slots 44, as illustrated in figure 4. Although the resultant vertical motion of the clamp arm 52 is only a few thousandths of an inch, this is sufficient clearance for operation and to allow for variation in the work pieces, and sufficient to generate the necessary downward clamping force.
The clamp block 50 is shown in more detail in figures 5-8. The clamp block 50 has an opening 51 to receive pin 42, a longitudinal bore 57 to receive one end of tension spring 55, and a cylindrical clamp arm 52 extending from clamp block 50, said clamp arm 52 having two perpendicularly surfaces 58, 59, respectively. The pivot 60 is shown in more detail in figures 9-11. The pivot has a central portion forming a bore 62 to receive the clamp arm 52, circular ends having grooves 63 to receive the end of a bolt (not shown) threaded through an opening 36 in the clamp body 30 to stabilize the pivot 60 inside the clamp body 30. The pivot is positioned in opening 32 of the clamp body 30 to rotatably cooperate with the clamp body and fluidly seal the end opposite the pneumatic cylinder 20.
The clamp body 30 is shown in more detail in figures 12-16. The clamp body 30 is elongated and rectangular having a bore 31 extending longitudinally, four openings 33 extending from the top through to the bottom of the clamp body 30 to receive bolts (not shown) to secure the clamp body to a work station. The clamp body 30 includes threaded bores 34 to receive the threaded ends 26 of bolts 25 to secure the pneumatic cylinder 20 longitudinally to the end of the clamp body 30. The clamp body 30 also includes a second threaded opening 36 to receive a screw (not shown) threaded into the clamp body 30 and extending into the groove 63 of the pivot 60 to secure the pivot 60 in the opening 32 of clamp body 30. The clamp body 30 also includes a carved out area 35 of the bore 31 to allow more room for the clamp block 50 to pivot as the piston rod 23 drives the clamp block 50.
The pneumatic cylinder 20 is shown in more detail in figures 17-18. The cylinder has two fluid ports 21 longitudinally spaced in each cylinder head 27 which are in fluid communication with the fluid chamber 28 within the pneumatic cylinder 20. A piston 22 is securely attached to a piston rod 23 which slidingly cooperating inside the fluid chamber 28 longitudinally. Elongated bolts 25 extend longitudinally through each head 27 and have threaded ends 26. The piston rod 23 also has a threaded end 24.
The clevis bracket 40 is shown in more detail in figures 19-23. The clevis bracket 40 has two arms 46 extending longitudinally and parallel to one another, each arm 46 having slots 44 to receive pin 42, with clevis bracket including a first longitudinal bore 43 to receive one end of tension spring 55 and a second threaded bore 41 to receive the threaded end 24 of the piston rod 23.
The small rectangular body of this power clamp with the pneumatic cylinder extending longitudinally from one end of the body with no greater dimensions than the clamp body, and the range of motion for the clamp arm not extending outside the longitudinal perimeter of the clamp body provides for a very low profile power clamp which greatly improves the accessibility of the workpiece to any tooling or other machining operations. Furthermore, the clamp body with the ends enclosed by the pneumatic cylinder and pivot piece at the opposite end seals the clamp body adequately enough to hold lubricating grease without the necessity of lubrication being provided through the fluid actuating means. This provides a clamp body bore with a clean environment preventing failure and the necessity of continued maintenance for the power clamp.
An alternate embodiment of the present invention is a low profile clamp shown in Figs. 24 and 25, whereby a modified clamping adaptor 70 is slidingly cooperating with clamp arm 52 at opening 71 and securely attached by a screw or bolt (not shown) positioned through a second opening 73 and into the clamp arm 52. The clamping adaptor 70 has a horizontal clamping surface 72 (which provides the vertical clamping force on the workpiece 80 in figure 24) which is positioned at or above the top horizontal surface 38 of the clamp 10 and the top horizontal surface 81 of the workpiece 80 which is also situated at or above the top horizontal surface 38 of the clamp 10. The workpiece 80 is located at or above the clamp surface 38 by raising the fixture holding the work piece, by lowering the position of the clamping mechanism, or by providing a work piece riser 82 as shown in Fig. 24. In this configuration, the only portion of the entire clamping mechanism which is exposed above the work piece surface 81 is the adaptor 70, which greatly improves the accessibility of the work piece 80 to any tooling or other machining operations.

Claims

A low profile clamp (10) comprising:

a clamp body (30) having a longitudinal bore (31) ;

a cylinder (20) having a fluid chamber (28) therein and removably attached to said clamp body along the longitudinal axis, said cylinder including a pair of fluid ports (21) longitudinally spaced from one another in fluid communication with said fluid chamber;

a bracket (40) slidingly held within the bore (31) of said clamp body (30);

a piston rod (23) longitudinally disposed in said bore (31) and having a first end (24) removably secured to said bracket;

a piston (22) removably attached to the piston rod (23) opposite the first end (24), said piston being sealingly disposed for slidable, longitudinal movement within said fluid chamber (28) between said fluid ports (21) in order to selectively extend and retract said piston rod longitudinally in response to respective greater and lesser fluid pressures in one of said fluid ports (21) with respect to the other of said fluid ports; and

a clamp block (50) slidingly held within the bore (31) of said clamp body (30), said clamp block having a first end held within the bracket (40) and slidingly cooperating along an angled path relative to the longitudinal motion of the bracket, said clamp block further including a clamp arm (52) extending from a second end and a portion protruding outside the clamp body.
The low profile clamp of claim 1, wherein said bracket (40) includes two arms (46) extending longitudinally, each arm having a slot (44) opposing and parallel to the other, said slots being angled relative to the longitudinal motion of said bracket.
The low profile clamp of claim 2, further including a pin (42) extending through said first end of said clamp block (50) and slidingly resting in said slots (44).
The low profile clamp of any one of the preceding claims, further including a pivot (60) rotatably held inside the clamp body (30) and sealing the bore (31) at the end of said clamp body opposite the cylinder (20), said clamp arm (52) being slidingly held in said pivot perpendicular to the rotation axis.
The low profile clamp of any one of the preceding claims, further including a biasing means (55) securely positioned between said bracket (40) and said clamp block (50) to force both longitudinally apart.
A low profile clamp as claimed in claim 1, wherein:

said clamp body (30) is elongated and has least one flat surface;

said bracket (40) is a clevis bracket and includes two arms (46) extending longitudinally, each arm having a slot (44) opposing and parallel to the other, said slots being angled relative to the longitudinal motion of said clevis bracket, said clevis bracket further including a first longitudinal opening (43);

said first end of said clamp block (50) has a pin (42) slidingly held within the slots (44) of said clevis bracket; and

wherein said clamp block (50) further includes a second longitudinal opening (57).
A low profile clamp as claimed in claim 6, further comprising:

a tension spring (55) securely held in said first and second openings (43, 57) of said clamp block (50) and clevis bracket (40) to force both longitudinally apart; and

a pivot (60) rotatably held inside the clamp body (30) and sealing the bore (31) at the end of said clamp body opposite the cylinder (20), said clamp arm being slidingly held in said pivot perpendicular to the rotation axis.
The low profile clamp of any one of the preceding claims, wherein said clamp arm (52) includes both vertical and horizontal clamping surfaces (58, 59).
The low profile clamp of any one of the preceding claims, wherein said piston is pneumatically powered.
The low profile clamp of any one of the preceding claims, further including a clamp adaptor (70) removably secured to said clamp arm (52), said clamp adaptor having a horizontal clamping surface (72) which is at a predetermined distance relative to the surface of the clamp body.