WO1993025448A1

WO1993025448A1 - Positive stop axial clamp

Info

Publication number: WO1993025448A1
Application number: PCT/US1993/005377
Authority: WO
Inventors: Charles W. Olson; Stephen R. Meyer; Paul T. Kibbe
Original assignee: Rosemount Inc.
Priority date: 1992-06-08
Filing date: 1993-06-07
Publication date: 1993-12-23

Abstract

A cam operated clamp (10) having a housing (11, 51) which changes its effective diameter due to the rotation of a cam (40) includes a stop (33, 55, 60) for stopping cam rotation when the clamp (10) is tightened. The cam pin (40) has a stop lug (45, 49) formed on one end, which abuts with a stop tab (33, 55, 60) formed on a cam journal (27, 29, 63, 64, 65, 66, 76, 78, 82, 84). When the stop lug (48, 49) abuts with the stop tab (33, 55, 60) as the cam (40) is rotated in a first direction, the clamp is in a maximum clamping position and cannot be rotated beyond the tightened position to a position wherein the clamp is loosened.

Description

POSITIVE STOP AXIAL CLAMP

BACKGROUND OF THE INVENTION The present invention relates to an improvement in a clamp for an injection molding heater that simply and easily provides clamping force to clamp a heater onto a cylindrical nozzle for heating the nozzle.

Nozzle heaters for injection molds are helically wound around the nozzles. The nozzles are recessed into cavities and access for tightening the heaters onto the nozzle is restricted. The ability to adjust the heater clamping force from the open end of the recess is desired, and this is accomplished in U.S. Patent No. 4,968,247. The clamp in U.S. Patent No. 4,968,247 does not have a positive stop and thus the operator may rotate the cam past the optimum tightening position.

SUMMARY OF THE INVENTION

The present invention relates to an improvement to a clamp for a heater used with injection nozzles, or other cylindrical objects or heaters, which utilizes a formed, generally cylindrical housing which has a slit or slot along a longitudinal line. A cam member is rotatably mounted on one side of the slit and an offset cam section is coupled to the clamp on the other side of the slit so that when rotated, the cam will urge the opposite edges of the slit together to tighten the clamp onto the heater. The cam and clamp are provided with cooperating stops to limit the rotation of the cam, which not only prevent going over center, but also provide positive indications of the cam in fully clamped and released positions. One of the cam supports has a stop tab which abuts with a stop portion of the rotatable cam member in the form disclosed. Friction between the rotatable cam member and the cam supports will hold the cam in place. Other stop arrangements can be used if desired.

A second embodiment of the invention utilizes dual cam members, each cam member is made as in the first embodiment, and each cam comprising positive stop indication means of desired clamping force as in the first embodiment. Each cam member is rotatably mounted in journals found on opposing edges of the clamp housing substantially as described in the first embodiment. A rigid linking member has cam journals formed at opposite ends thereof. The journals on the linking member are mounted on the center portions of the respective cam members and maintain the cam members at a constant distance from the other. Rotation of the cam members urges the opposing edges of the housing slit together, thereby tightening the clamp onto the heater. Each cam member has cooperating stops to limit rotation and to provide an indication of fully clamped and released positions. The use of two cams increases the range of tightening movement available.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevational view of a heater clamp housing made according to the present invention shown in place on an injection nozzle, with parts in sectional and parts broken away; Figure 2 is a sectional view taken along line 2—2 in Figure 1;

Figure 3 is a top plan view of the heater clamp housing; Figure 4 is a flat layout of the clamp housing before forming it into its clamp shape;

Figure 5 is an end elevational view of the cam in an unlocked position;

Figure 6 is a side elevational view of the cam pin shown in place in journals;

Figure 7 is an end view of the cam as shown in Figure 5 but in a stopped, clamp tightening position; Figure 8 is an end elevational view of an alternative embodiment of the cam pin;

Figure 9 is a side elevational view of a heater clamp housing made according to the second embodiment of the present invention; Figure 10 is an end elevational view of the second embodiment of the present invention;

Figure 11 is a flat layout of the clamp housing of the second embodiment of the present invention before forming it into its cylindrical clamp shape;

Figure 12 is a sectional view taken along line 12—12 in Figure 9. Figure 13 is an end elevational view of a third embodiment of the present invention; and

Figure 14 is a sectional view similar to Figure 12 but having the linking member of the third embodiment.

Figure 15 is a sectional view similar to Figure 12 but having the linking member of a fourth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A heater clamp indicated generally at 10 includes a clamp housing 11 which surrounds a heater element 12. The heater element 12 is a helically wound heater of a type well known and is described in more detail in U.S. Patent No. 4,968,247.

The housing 11 is formed from a flat sheet, as seen in Figure 4, and is formed with an integral U shaped member 25 at one edge thereof and an integral T shaped member 26 at the other edge. The U shaped member 25 has a pair of straps 27 and 29 which are spaced apart, and a connecting end member 28 that joins the straps 27 and 29. A stop tab 33 is formed on strap 27. The T shaped member 26 has a central cam follower web 30 and a T end 31 at the outer end thereof. When the housing 11 is made, the main portion is formed into a cylindrical shape while leaving a slit 16 between the edges of the housing. The U shaped portion 25 is rolled or formed in an opposite direction from the cylindrical forming, so that the end member 28 is doubled back onto the adjacent edge portion of the housing, with the straps 27 and 29 being formed into cylindrical journals. The end member 28 is formed down against the outer surface of the cylindrical housing 11 and is tack welded in place. The strap 27 is narrower than the strap 29 throughout most of its length and has a stop tab 33 formed on one edge that protrudes outwardly from the strap. The tab 33 is positioned at a desired rotational position around the journal as can be seen in Figure 5.

The T shaped member 26 is also formed back in an opposite direction from the cylindrical forming of the main portion of the housing 11 and the center cam follower web 30 is formed to be of size specifically to fit over a cam portion 42 of a pin 40 that is used for adjusting the clamping action of housing 11. The T end 31 is then tack welded down onto the outer surface of the housing.

The cam follower web 30 fits in between straps 27 and 29, and the bore formed by the formed cam follower web 30 and the journals formed by straps 27 and 29 interfit. The cam pin 40 has hub ends 41 and 43 that are of size to fit into the journals formed by the straps 27 and 29 and rotate therein. The cam loop formed by web 30 fits over a cam center portion 42 of the cam pin 40. The cam center portion 42 is between hubs 41 and 43, and is formed by making a recess in the cam center portion between hubs 41 and 43 and leaving a cylindrical center portion.

As can be seen in Figure 6 in particular, hubs 41 and 43 have a central axis 44. Rotating cam pin 40 about central axis 44 causes the cam center portion 42 to change its effective radial position relative to the central axis 44. The cam action tightens the clamp by decreasing the width of slot 16 and thus the diameter of housing 11 to tighten the housing with respect to the heater element 12. Reverse movement of the cam causes the clamp to loosen.

A stop lug 45 is positioned on one end of hub 43 as can be seen in Figures 5 and 6. The lug 45 extends radially outwardly beyond the periphery of the hub 43, and extends annularly part way around the circumference. The lug 45 is also positioned to the exterior end of the hub 43, so that hub 43 can turn in the journal formed by the strap 27. The tab 33 protrudes into the path of movement of the stop lug 45 as the cam is rotated in either direction. In a first direction, counterclockwise as shown in Figure 5, the first edge 45 A will engage the tab 33 and stop rotation of the cam when the cam has tightened the clamp housing to the maximum, which is seen in Figure 7. The edge 45B will strike the tab 33 when the cam is rotated in a second direction, with the cam in a loosened position. Stop lug 45 extends around approximately one-third of the circumference of the hub 43. In operation, with the clamp housing 11 surrounding a heater element 12 as seen in Figure 1, a tool or wrench 47 is inserted into a drive recess 48 in the end of either hub 41 or 43. By turning the wrench 47 cam pin 40 is rotated, thus increasing or decreasing the width of slot 16 under a cam action. Rotating cam pin 40 in the first direction until stop portion 45 abuts stop tab 33 results in clamp housing 11 being in a maximum clamping position. By rotating cam pin 40 in the second direction until stop portion 45 abuts the stop tab 33, the clamp housing 11 ends up in a minimum clamping position.

An alternative design for the stop lug is shown in Figure 8. A stop lug 49, shown in Figure 8, is a radial pin or stud which replaces the shoulder configuration of the first embodiment. When stop lug 49 abuts an aligning tab on the clamp housing 11, it is in its maximum clamping position.

The tab engaged by the lug 49 does not have to be on the journal strap. The lug 49 can be positioned relative to the center portion 42 of the cam so that it strikes the housing surface and is stopped in a maximum tightened position. If provided with side clearance to clear web 30, the stop lug 49 could also be located on the center portion 42 of the cam to be stopped on a tab formed on web 30.

In a second embodiment of the present invention, dual cam members are each rotatably connected to the clamp housing with parallel journals substantially as the single cam is connected in the first embodiment. However, in the second embodiment, a linking member having journals at opposite ends rotatably connects between the dual cam members in place of the central cam follower web of the first embodiment. The clamp housing 51 is formed from a flat sheet, as seen in

Figure 11, and is symmetrically patterned with opposing integral U-shaped portions 52 and 53 similar to the U-shaped portion of the first embodiment. Each U-shaped portion is rolled or formed in an opposite direction from the cylindrical forming so that each end member 54 and 61 is doubled back onto an adjacent outer surface portion of the housing 51 with strap portions 56 and 57 as well as 59 and 62 being formed into cylindrical journals 63 on one edge and 64 on the other edge for receiving the cam members. Each end portion 54 and 61 is formed down against the outer surface of the housing 51 and is tack welded in place. Strap portions 57 and 59 have stop tabs 55 and 60, respectively, formed on one edge that protrudes outwardly from the respective strap portion. Each stop tab 55 and 60 is positioned at a desired rotational position around each journal as can be seen in Figure 10. The aligning cylindrical journal 63 and 64 formed on the opposite edges rotatably receive separate cam members, respectively. The cam members 40 are the same as the cam member 40 shown in Figure 6. Each cam member has hubs 41 and 43, a cam center portion 42 and at least one drive recess 48 for receiving a drive member 47. Each cam member 40 is provided with stop means for indicating a maximum clamping force position. Each cam member may be provided with either a stop lug 45 positioned on the exterior end of hub 43 as seen in Figures 5 and 6 or the alternative design for the stop lug as shown in Figure 8 comprising a radial pin or stud replacing the shoulder configuration of the primary design.

The cam members, when they are rotated in the journal 63 and 64 on the opposite edges of the split clamp, are aligned with each other so that the cam center portions are in alignment. A linking member 58 is made to be of a width substantially equal to that of the axial length of the cam center portions 42. The linking member 58 has opposite ends that are rolled to form journals 65 and 66 at opposite ends thereof which fit over the cam center portions 42 of the respective cams on opposite side edges of the clamp. The cam can rotate inside the journal 65 and 66, so that as the cams are rotated the spacing between the edges of the clamp will be changed as previously described. Because two cams are utilized, the adjustment or travel of the two edges is doubled, so that additional clamping travel can be obtained. As shown in Figure 10, the lug members 45 of the two cams are positioned so that one edge of the lug contacts the stop member 55 formed as part of the journal 63, and the other lug member on the cam contacts the lug 60 that is formed as part of the journal 64. Cams are rotated in opposite direction to obtain a maximum tightening position as shown in Figure 10. This position is also shown in Figure 12, which is a sectional view through the center portions of the cam members.

To loosen the unit, the cams are merely rotated substantially 180 degrees to their loosened position for installation or removal of the clamp.

The stops on the clamp increases the ease of using the clamp because it insures that the cam does not go over center but yet it will be clamped in the maximum tightened position. A variety of different stop lugs and stop tabs or surfaces can be used.

A third alternative embodiment has a modified linking member 70 which replaces the linking member 58 of the second alternative embodiment. Linking member 70 has a "dog-bone" shape. Figures 13 and 14 show the clamp housing as illustrated for the second alternative embodiment except the linking member 70 is used. The element numbers in Figures 13 and 14, therefore, correspond to the elements in Figures 11 and 12. A solid load-carrying strap 72 is provided on the linking member 70. Cylindrical journals 76 and 78, in which cam center portions 42 rotate, are connected to the load carrying strap 72 at its ends. The cylindrical journals 76 and 78 are formed closely around the cam center portions 42 and are sized to allow the cam center portions 42 to rotate therein. The assembly procedures are such that the journals 76 and 78 can be left open for assembly over the cam center portion after the hubs of the cam have been positioned in the respective straps 56,57 and 59,60. The journals then can be closed. When in a tightened position, as shown in Figure 14, cam center portions 42 seat in the cylindrical journals 76 and 78, thus applying force onto the cylindrical journals 76 and 78 tending to close the clamp. The load-carrying strap 72 is of sufficient size to withstand this force. Stops are also used with this embodiment, as previously described.

The second and third embodiments also provide a separating force which helps unseat the clamp housing. If the clamp housing becomes corroded or covered with foreign matter, a separating force may be necessary to loosen the clamp housing. By rotating the cam members 40 in a loosening direction, the cam center portions 42 rotate from abutting outer portions of the cylindrical journals of the cam linking members to abutting inner portions, or adjacent portions, of the cylindrical journals of the cam linking members wherein a separating force across the housing slit results.

A fourth embodiment, which is shown in Figure 15, has a further modified linking member 80 which replaces the linking member 70 of the third embodiment. Linking member 80 has a "figure-8" configuration which was chosen because of the ease of manufacturing. As in Figure 14, the element numbers in Figure 15 correspond to the elements in Figure 12 except for the linking member.

The linking member 80 may be formed from a continuous loop or strap which has two cylindrical journals 82 and 84 formed at its ends with strap portions between the journals. The cylindrical journals 82 and 84 are sized to allow the hubs of cam members 40 to be inserted endwise through the journals 82 and 84. The cam members 40 are held in place when the journals 82 and 84 seat on the cam center portions 42 due to the tendency of the clamp housing to spring open. When in a tightened position, as shown in Figure 15, cam center portions 42 seat in the cylindrical journals 82 and 84, thus applying force onto the cylindrical journals 82 and 84 tending to close the clamp. A suitable stop can be provided as in the other embodiments.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A cam operated clamp comprising: a clamp housing for substantially surrounding a member to be clamped and being tightenable by urging adjacent edges together; a rotatable cam member having a first portion rotatably mounted relative to one of the adjacent edges and a second eccentric portion, means to connect the second eccentric portion to another of the adjacent edges whereby rotating the cam causes the edges to be moved together; and stop means cooperating between the housing and the cam member to limit the rotation of the cam member.

2. The clamp of claim 1 wherein the means for rotatably mounting the cam member is provided and comprise a pair of journals that are on the housing that are spaced apart, one of said journals having a stop tab thereon, and a portion of said cam member positioned to engage the stop tab at a pre¬ selected rotational position of the cam.

3. The clamp as specified in claim 2 wherein the portion of said cam member positioned to engage the stop tab is a stop lug.

4. TRe clamp as claimed in claim 1 wherein said rotatable cam member's first portion comprises spaced hubs and the second eccentric portion comprising a smaller central portion having a central axis offset from a rotatable axis of the hubs, the central portion of said cam member changing its effective position relative to the rotatable axis when the cam member is rotated.

5. The clamp as claimed in claim 1 wherein said stop means of said rotatable cam member is a stop lug formed at one end of a hub on the cam, said hub being mounted in a journal having the stop lug thereon, the lug extending radially outwardly from the hub and having a first end facing in a direction of rotation of the cam, the first end of the stop lug abutting a tab at a pre-selected rotational position, which is a clamping position, and wherein rotating the cam in a second direction causes a second end of the stop lug to abut the tab at a release position.

6. The clamp as claimed in claim 1 wherein the means to connect the second eccentric portion to another of the adjacent edges comprises a link having a first end rotatably mounted on the second eccentric portion of the rotatable cam member and means to retain a second end of the link relative to the second edge.

7. The clamp as claimed in claim 6 wherein said means to retain the second end of the link comprises a second rotatable cam member mounted adjacent the second edge and having a cam portion, the second end of the link being connected to said cam portion.

8. A cam operated clamp comprising: a clamp housing member that is formed generally into a cylindrical shape to receive a member to be clamped and being tightenable by urging adjacent edges together; a pair of cam members each provided with a first portion rotatably mounted to opposing adjacent edges of the housing each provided with a second cam portion; a linking member rotatably connected between the second cam portions of the pair of cams; and stop means cooperating between the clamp housing and the cam members to limit the rotation of the cam members.

9. The clamp of claim 8 wherein each cam member is rotatably mounted in a pair of journals that are spaced apart on the housing.

10. The clamp of claim 9 wherein the stop means comprise a stop tab on at least one journal on each of the opposite edges, and a portion of each of the respective cam members positioned to engage the corresponding stop tab at a preselected rotational position of the cam.