MX2008010031A - Improved hydraulic damper valve - Google Patents

Abstract

A breakstem rivet placing tool conventionally includes a flow restrictions (14) for hydraulic fluid used to drive the tool in a stem pulling direction. This serves to prevent recoil of the tool due to rapid acceleration of an internal piston (4) when the stem of the breakstem rivet breaks. Prior art flow restrictions (14) create a jet (10) of high velocity hydraulic fluid into the tool which may damage components (26) by erosion. A revised fluid damper valve (14',14'',14''',40,42,42âÇ) deflects and/or diffuses the fluid flow to avoid damage by erosion.

Description

IMPROVED HYDRAULIC CUSHION VALVE This invention relates to an improved hydraulic damping valve and in particular to said valve for use with a hydropneumatically operated riveting tool for fasteners with breakable shank. Figure 1 shows a rivet setting tool known in the prior art. The tool has fastening means (not shown) which cooperate with a hydraulic piston arrangement 4 for clamping and pulling the shank of a breakable shank fastener in the manner known in the art. The clamping means pulls the rod in the direction shown by the arrow 'A' when the hydraulic fluid enters an inlet port 6 of the cylinder 8 associated with the piston 4. As is known in the art, the pull of the rivet shank it eventually results in rupture of the stem to leave the rivet placed behind. At the moment of the rod breaking, the tensile load required on the clamping means rapidly decreases. To prevent rapid acceleration of the piston 4 backward, a flow restriction is conventionally placed in the hydraulic fluid path within the tool to produce a decrease in hydraulic pressure in the cylinder 8 thus while the piston 4 attempts to accelerate. In this way the flow restriction has the effect of dampening the backward movement of the piston 4 which is made for a more comfortable operation and for improve the useful life of the tool. Figures 2A and 2B show an enlargement of the area around the inlet port 6. The dotted thick line 10 shows the general direction of the hydraulic flow within the tool during the traction operation. After pulling, the piston and the clamping means return to a previous rest position ready for another rivet replacement, under the action of spring and / or pneumatic as is known in the art. As this occurs, the hydraulic fluids flow out of port 6 in a direction opposite to that indicated by arrow 10. Therefore, in use, hydraulic fluids flow in both directions through port 6 as indicated by of the arrow 12 in Figure 1. Accordingly, in a conventional manner, a movable member 14 is held near the inlet port 6 by means of ridges 16 (which restrict the outward movement of the member remote from the tool during the flow outwardly of the hydraulic fluid) and a sealing region 18 around the periphery of the inlet port 6 In Figure 2A, the mobile member 14 is shown in an unsealed position in which an inner surface 20 of the mobile member 14 is maintained away from the sealing region 18, against the flanges 16, by means of the flow of the hydraulic fluid. In this position, the fluid is free to flow around the periphery of the movable member 14 under the cuts 22. Therefore, while the clamping means and piston 4 return to the rest position, the flow of hydraulic fluid leaving port 6 is not greatly restricted. However, when the fluid flows in the opposite direction (as shown by arrow 10), the movable member 14 is urged such that its inner surface 20 rests against the sealing surface 18 around the periphery of the inlet. of the port 6. This has the effect of preventing fluid from flowing around the periphery of the movable member 14 so that the fluid can only flow through a central opening 24. The opening 24 is positioned to have a transverse flow area greatly reduced relative to the cutting portions 18. Thus when pulling the stem or rivet, fluid can only flow through the restricted opening 24 within the tool. This flow restriction provides the damping effect described above. However, the restriction of the flow also increases the flow velocity and thus creates a jet of fluid within the inlet port 6 of the tool. In the example shown in figure 2A, this jet (denoted by the arrow 10) strikes directly on an elastomer seal 26. This is not desirable since the high velocity of the jet can reduce the operational life time of the seal 26 by erosion effects. Accordingly, it is an object of the present invention to provide a damping effect during the pulling of the shank of a rivet with breakable shank while avoiding damaging the parts vulnerable internal members of the placement tool. In a first aspect, the invention provides a hydro-pneumatically operated riveting tool, whose tool includes fastening means hydraulically driven by fastening and pulling the shank of a rivet, in order to place the rivet, a hydraulic inlet port in order to supply hydraulic fluid for handling the fastening means, a sealing region around the inlet port and return means for returning the fastening means to a rest position again after placing a rivet, the hydraulic supply for the fastening means including a unidirectional flow restriction positioned to provide a restricted flow of hydraulic fluid during stem traction and to provide a relatively free flow during the return of the securing means to a resting position, the flow restriction comprises a movable member located at the trajectory of the adjacent hydraulic flow the inlet port which is positioned to have a reciprocal movement limited in the direction of the hydraulic flow to and away from the inlet port within a sealed and unsealed position, the movable member having an internal surface which cooperates with the sealing region around the inlet port to form a seal which substantially prevents the flow of hydraulic oil around the periphery of the movable member when the member is pushed by the hydraulic flow into the sealing position the movable member includes a relatively small cross-flow area opening through which hydraulic fluid is allowed to flow when the movable member is in the sealing position, the movable member which is positioned to diffuse or direct hydraulic flow through the opening away from the components susceptible to erosion which are in the vicinity of the port of entry. In a further aspect, the invention provides a movable member for use in the tool of the first aspect. The embodiments of the invention will now be described by way of example and with reference to the drawings in which: Figure 1 is a section through a rivet setting tool as is known in the prior art; Figure 2A is an elongation of Figure 1 in the region of a hydraulic inlet port; Figure 2B is a section through Figure 2A along the line ll-ll; Figure 3A is a view corresponding to that of Figure 2A showing a new moving member according to the invention; Figure 3B is a sectional view along the line III-III of Figure 3A; Figure 4A is a view corresponding to that of Figure 3A showing a new moving member according to the invention; Figure 4B is a sectional view along the line IV-IV of Figure 4A; Figure 5A is a view corresponding to that of Figure 4A showing a new moving member according to the invention; Figure 5B is a sectional view along the line V-V of Figure 5A; Figure 6A shows a view similar to Figure 2A although it includes a diffuser component according to the present invention; Figure 6B is a section along the line VI-VI of Figure 6A; Figure 7A is an elevation of a seal fastener according to the invention; Figure 7B is a section along the line VII-VII of Figure 7A; Figure 8A is an elevation of an alternative seal fastener; and Figure 8B shows several alternative sectional configurations along lines VIII-VIII of Figure 8a. With reference to Figures 3A and 3B, in a first embodiment, a mobile member 14 'has a port 24', offset from the center of the member 14 '. The mobile member 14 'is shown in an unsealed position. A bore hole 28 is formed to allow fluid to flow in a direction generally indicated by arrow 10. It will be noted that the fluid flows during the pulling of the shank that now follows a complicated trajectory since the opening 24 'is deliberately misaligned with port 6. This has the effect of reducing the flow velocity as it enters port 6. The material forming the periphery of the inlet port 6 is typically hard anodized aluminum. Thus at point 30 on which it is impacted by jet 10, it is able to resist erosion. In addition, any erosion that occurs at this point does not impair the operation of the tool. Preferably, the reaming hole 28 is formed on both sides of the member 14 'so that the member can be assembled in any orientation. Furthermore, it will be appreciated that the movable member is free to rotate although the selection of the position of the port 24 'is such that even after rotation it will always direct the flow of fluid around the periphery of port 6 instead of going directly towards port. Accordingly, the embodiment shown in Figures 3A and 3B is a convenient retrofit to the tool of the primary technique and solves the problem of erosion of delicate components within the tool and inside port 6. With reference to Figures 4A and 4B, an alternative mobile member plus 14"is shown." Again, member 14"is shown in an unsealed position. In this embodiment, a side port 34 forms an inlet within the movable member 14"which then feeds a generally elongated central outlet port 36. The outlet port is in coincidence with the port of entry of the tool 6 but has a cross-sectional area much larger than the lateral port 34. Therefore as the fluid makes the transition from the lateral port 34 to the exit port 36, the increase in the area Transverse flow results in a reduction in fluid velocity. Consequently, the erosion of delicate components within the inlet port 6 is prevented through a reduction in the fluid flow rate while still maintaining the flow restriction necessary for the damping operation of the tool during the traction of the shank . With reference to Figures 5A and 5B, there is shown an alternative mobile member 14"'more.In this embodiment an opening 24"' is formed through a movable member 14"'at an angle in the direction of fluid flow within of the inlet port 6. This causes the flow of the fluid 10"'to be directed against a rigid side wall region 38 of the inlet port 6. The region 38 is not critical and is generally resistant to erosion. Having impacted region 38, the fluid is dispersed and the velocity is reduced as it passes upward into the most delicate parts of the tool. Consequently, any problem with erosion is avoided. In addition, preferably the angled port 24"'is angled symmetrically about a centerline of the movable member 14"' so that it can be installed in any orientation during the assembly of the tool. It will be observed by With FIGS. 3A and 3B, this mode does not require a bore hole 28 since the output from the mobile member on its internal surface adjacent to the inlet port 6 is in conjunction with a register with the port of communication. entry 6. This modality is also a convenient retrofit for existing tools. With reference to Figure 6A and 6B, a diffuser or baffle 40 can be inserted into the inlet port 6 to reduce the velocity of the fluid in a manner similar to the embodiment shown in Figure 5A and 5B. It can be used with the mobile member 1 4 of the previous technique. Advantageously, the baffle can be formed as a revised (beveled) portion of a fastener with r 42 already present in the tool (see FIG. 7A). This fastener or other similar component is used to maintain the seal 26 in its place. By providing a bevel 44, the flow of the fluid 1 0 is deflected and reflected at a reduced speed within the tool 6 and thus avoiding any problem with erosion. Figures 8A and 8B show alternative configurations in which 46, 46 '46"serve to capture the flow of the fluid 1 0 and reflect it back at a reduced speed, and again these components are a simple retrofit of the existing tools. Therefore, the components described above can conveniently be retro-adapted to existing tools and serve to deflect or redirect high-speed fluid flows. created by a flow restriction used to dampen during stem traction. The deflection, diffusion or redirection serves to prevent the erosion of vulnerable parts in the vicinity of the port of entry.

Claims (4)

1. A hydro-pneumatically operated riveting tool, which includes hydraulically operated fastening means for fastening and pulling the shank of a rivet, to thereby place the rivet, a hydraulic inlet port for supplying hydraulic fluid to handle the clamping means, a sealing region around the inlet port, and return means for returning the securing means to a rest position again after placing a rivet; the hydraulic supply for the fastening means including a unidirectional flow restriction positioned to provide a restricted flow of hydraulic fluid during the traction of the stem and provide a relatively free flow during the return of the fastening means to a resting position, the flow restriction comprising a movable member located in the hydraulic flow path adjacent the inlet port which is positioned to have a limited reciprocal movement in the direction of the hydraulic flow to and away from the inlet port within a sealing position and without sealing, the movable member has an inner surface which cooperates with the sealing region around the inlet port to form a seal which substantially prevents the flow of hydraulic oil around the periphery of the movable member when the member is pushed by the hydraulic flow within the position of sel side, the mobile member which includes an opening of a relatively small cross-flow area through which the hydraulic fluid is allowed to flow when the movable member is in the sealing position, the movable member which is positioned to diffuse or direct the hydraulic flow through of the opening away from the components susceptible to erosion which are in the vicinity of the entrance port

2. A tool according to claim 1, characterized in that the opening is generally formed in coincidence with a region immediately outside the periphery of the port inlet and wherein the inner surface of the member is released adjacent to the opening to prevent sealing of the inner surface against the sealing surface in the region of the opening and to provide a convolutional path for hydraulic flow through the opening and passing the released region when the member is in a sealing position. A tool according to claim 1, characterized in that the opening is formed as a generally linear passage at an angle in the direction of a hydraulic flow so that the restricted flow through the opening to the inlet port is directed on the side wall of the entrance port. 4 - A tool according to claim 1, characterized in that the opening has a member entrance on the side of the movable member and a member exit on the surface internal, member entry and member exit that are joined by an internal passage that has a convolutional path within the member. 5 - A tool according to claim 4, characterized in that the entry of the member has a smaller cross-sectional area than the exit of the member and in which the outlet is generally in coincidence with the hydraulic inlet port. 6. A tool according to claim 1, characterized in that the member is positioned to direct the hydraulic flow through the opening towards a diffuser component placed in the inlet port near the movable member. 7 - A tool according to claim 6, characterized in that the diffusing component includes a deflection surface which is non-parallel and not orthogonal with the side walls of the inlet port and which deflect the received flow through the opening away of the components susceptible to erosion in the port of entry. 8 - A tool according to claim 6, characterized in that the diffusing component includes a recessed portion positioned to capture and reflect the flow through the opening to thereby reduce the flow velocity. 9. A movable member for use in the tool according to any of claims 1 to 8, the movable member that is positioned to have a limited reciprocal movement in the direction of hydraulic flow to and away from the inlet port in a sealed and unsealed position. A member according to claim 9, comprising a disc having a larger face positioned to seal against a sealing region of an inlet port of a rivet setting tool and an opening passing between both larger faces of the disc which is offset from the center of the disk 11. A member according to claim 9, comprising a disk having a larger face positioned to seal against a sealing region of an inlet port of a rivet setting tool and a flow restriction port that passes between the larger sides of the disk, the port that passes through the disk in a direction not parallel to the disk axis. A member according to claim 10 or claim 11, comprising a disc having a first major face positioned to seal against a sealing region of an inlet port of a rivet setting tool, and an inlet opening on one side of the disk in fluid communication with an exit opening on the first major face of the disk. A member according to claim 12, characterized in that the inlet opening has a cross-sectional area smaller than the outlet opening. 14. - A tool constructed and positioned as described herein with reference to the drawings. - A mobile member constructed and positioned as described with reference to the drawings.