GB2402188A

GB2402188A - Hydraulic fastener assembly

Info

Publication number: GB2402188A
Application number: GB0312206A
Authority: GB
Inventors: John Hirst
Original assignee: Team Innovation Ltd
Current assignee: Team Innovation Ltd
Priority date: 2003-05-28
Filing date: 2003-05-28
Publication date: 2004-12-01
Anticipated expiration: 2023-05-28
Also published as: GB0312206D0; WO2004106756A1; GB2402188B; EP1664556A1

Abstract

A hydraulic fastener assembly includes a stud (1) that includes a screw threaded end portion, a screw member (5) around the stud and a sliding member (6) on an axially inner side of the screw member (5) slidably mounted on the stud (1). The arrangement is such that when in use the hydraulic fluid is passed into the assembly the sliding member (6) is pressed axially inwardly and hydraulic pressure forces on the screw member (5) are substantially balanced axially thereby facilitating screwing of the screw member (5) axially along the stud (1) towards the sliding member (6).

Description

24021 88 - 1 Fastener Assembly This invention relates to a hydraulic

fastener assembly and to a method of operating an assembly.

According to the invention there is provided a hydraulic fastener assembly including a stud that includes a screw threaded end portion, a screw member around the stud and a sliding member on an axially inner side of the screw member slidably mounted on the stud, the arrangement being such that when in use hydraulic fluid is passed into the assembly the sliding member is pressed axially inwardly and hydraulic pressure forces on the screw member are substantially balanced axially thereby facilitating screwing of the screw member axially along the stud towards the sliding member.

The balancing of the axially directed hydraulic pressure forces on the screw member enables the assembly to be of simple and compact construction. Furthermore, the construction is able to result in the screw thread of the screw member being within a sealed enclosure.

Preferably the screw member threadingly engages the screw threaded end portion of the stud.

Preferably the sliding member slidably engages the screw member. A seal is preferably provided between the sliding member and the screw member and another seal is preferably provided between the sliding member and the stud.

The sliding member is preferably able to slide axially - 2 - along the stud with no rotary movement. That is advantageous because in use the sliding member engages the workpiece that is clamped by the fastener assembly. The sliding member preferably comprises a piston partly received within a first recess on the axially inner side of the screw member, the one or more passageways in the screw member opening into the first recess.

The assembly preferably further includes an end stop member on an axially outer side of the screw member and in axially fixed relationship to the end portion of the stud.

A seal is preferably provided between the screw member and the end stop member. The end stop member is preferably received at least partly within a second recess on the outer side of the screw member, the one or more passageways in the screw member opening into the second recess. The end stop member may be free to rotate on the stud but preferably it is immovably fixed to the stud. It may for example be screwed onto the stud and bonded to the stud by adhesive. The end stop member is preferably an end cap completely enclosing the end of the stud.

The screw member is preferably provided with one or more formations, for example blind holes extending radially inwardly from a circumferential portion of the screw member, for receiving a tool for rotating the screw member.

In order to operate the fastener assembly, hydraulic fluid is passed into the one or more passageways in the assembly and a port is therefore preferably provided for enabling hydraulic fluid to be passed into the one or more passageways. The port is preferably provided in the end stop member, preferably on an outer end face thereof. The port may comprise a nipple for connection to a grease gun.

According to the invention there is further provided in a preferred embodiment a hydraulic fastener assembly comprising a stud including a screw threaded end portion, a screw member screw threadingly engaging the screw threaded end portion of the stud, an end stop member on an axially outer side of the screw member and in axially fixed relationship to the end portion of the stud, and a sliding member on an axially inner side of the screw member slidably mounted on the stud and slidably engaging the screw member, the screw member including one or more passageways extending from one side of the screw member to the other to provide fluid communication between the inner and outer sides of the screw member.

The invention still further provides a method of operating a hydraulic fastener assembly as defined above, the method including the steps of: introducing hydraulic fluid into the assembly to cause the sliding member to move axially inwardly away from the screw member; and subsequently screwing the screw member axially along the stud towards the sliding member.

Screwing of the screw member is facilitated by the equalizing of the axial hydraulic pressure forces on the screw member.

The screw member is preferably screwed along the screw threaded end portion of the stud until it abuts the sliding - member.

Whilst the stud may take any of a wide variety of forms depending on the particular application of the - invention, most commonly it will comprise a rod with a plain middle portion and opposite screw threaded end portions. In such a case and in the preferred embodiment, the end stop member, screw member and sliding member will first be installed on one end of the stud with the screw - member screwed to a position close to or abutting the end - stop member, the other end of the stud will then be passed through the workpiece(s) on which the assembly is to be fastened and a nut will then be secured to the other end of the stud and screwed onto the stud until it abuts the workpiece(s). The assembly may then be operated as defined above to clamp the workpiece(s) between the nut and the - sliding member with a clamping force determined by the hydraulic pressure applied and without requiring rotary movement of the nut or the sliding member relative to the - workpiece(s).

By way of example, an embodiment of the invention will now be described with reference to the accompanying drawings, of which: - Fig. 1 is an exploded perspective view of a stud fastener assembly; and Figs. 2a, 2b and 2c are schematic, sectional side views showing the operation of the assembly.

The stud fastener assembly comprises a stud 1 threaded - 5 along opposite end portions 2 and 3, an end cap 4, a cylinder 5 and a piston 6.

The end cap 4 is screwed over the end portion 2 of the stud 1 and is bonded thereto, for example by adhesive. A grease nipple 7 is provided on the exterior end face of the end cap and a passageway 8 connects the grease nipple to the interior of the cap 4.

The cylinder 5 is formed with a first recess 9 on the axially inner side of the cylinder and with a second recess 10 on the axially outer side of the cylinder. Situated between the recesses of the cylinder 5 is a middle portion 11 which has an internally screw threaded axial bore and screw threadingly engages the end portion 2 of the stud 1.

One or more passageways 17 (only one is shown in the drawings but more may be provided if desired) pass through the middle portion 11 of the cylinder 5, parallel to the axis of the assembly, and open into the recesses 9, 10 thereby providing free fluid communication between the opposite sides of the cylinder 5.

The piston 6 is partly received in the first recess 9 of the cylinder 5 and has a plain axial bore which is a slide fit on the middle portion 12 of the stud 1.

As seen best in Figs. 2a to 2c, the piston 6 has a circumferential recess in its axial bore receiving an 0 ring 13 that provides a seal between the piston and the stud 1, the piston 6 also has a circumferential recess in its outer circumferential surface receiving an 0 ring 14 that provides a seal between the piston and the cylinder 5, 6 - and the end cap 4 has a circumferential recess in its outer circumferential surface receiving an O ring 15 that provides a seal between the end cap 4 and the cylinder 5.

The cylinder 5 is formed with a radially extending blind bore 16 for receiving a tool such as a tommy bar for rotating the cylinder 5.

The operation of the assembly will now be described with reference to Figs. 2a to 2c.

The piston 6, cylinder 5 and the end cap 4 are first installed on the stud 1 as shown in Fig. 2a, with the cylinder 5 screwed to a position abutting the end cap 4.

The opposite end portion 3 of the stud 1 is then inserted through aligned bores in workplaces (not shown) that are to be fastened together and a nut (not shown) screwed onto the end portion 3 in a conventional manner and screwed up until there is little or no play between the fastener assembly and the workpieces.

A grease gun is then connected to the nipple 7 and grease is pumped into the end cap 4 until the pressure of the grease reaches a predetermined pressure. As the grease is pumped into the end cap 4, it passes through the one or more passageways 17 into the region between the piston 6 and the cylinder 5, thereby driving the piston 6 along the stud 1 away from the cylinder 5. Grease continues to flow until the force exerted on the workpieces by the piston reaches a predetermined value. At that stage, the piston 6, cylinder 5 and end cap 4 are in the positions shown in Fig 2b.

The cylinder 5 is then screwed along the stud 1 until it comes into abutment with the piston 6. (This step can be carried out with the grease gun connected or disconnected). During this operation grease flows back through the passageways 17 into the region between the end cap 4 and the cylinder 5. Screwing of the cylinder 5 is relatively easy since the hydraulic pressure is the same on both sides of the cylinder. Once the screwing of the cylinder is complete the grease gun is removed and the clamping pressure applied by the fastening assembly obtained from the mechanical pressure applied to the piston 6 by the cylinder 5, rather than the hydraulic pressure of the grease. The grease is retained within the fastener assembly and lubricates the screw connections between the cylinder 5, end cap 4 and the stud 1.

Whilst one particular embodiment of the invention has been described, it should be understood that many modifications may be made to the described embodiment. For example, rather than using a grease gun to supply the hydraulic fluid for the assembly, some other supply arrangement may be employed; that may be particularly desirable if the assembly is one of several operating together to clamp workplaces together, for example around a flange, because it may be desirable to connect several assemblies to the same hydraulic supply and thereby obtain even and simultaneous clamping by the assemblies. - 8

Claims

Claims 1. A hydraulic fastener assembly including a stud that includes a

screw threaded end portion, a screw member around the stud and a sliding member on an axially inner side of the screw member slidably mounted on the stud, the arrangement being such that when in use hydraulic fluid is passed into the assembly the sliding member is pressed axially inwardly and hydraulic pressure forces on the screw member are substantially balanced axially thereby facilitating screwing of the screw member axially along the stud towards the sliding member.
2. An assembly according to claim 1, in which the screw member threadingly engages the screw threaded end portion of the stud.
3. An assembly according to claim 1 or 2, in which the sliding member slidably engages the screw member.
4. An assembly according to claim 3, in which the sliding member comprises a piston partly received within a first recess on the axially inner side of the screw member, one or more passageways in the screw member opening into the first recess.
5. An assembly according to any preceding claim, in which the assembly further includes an end stop member on an axially outer side of the screw member and in axially fixed relationship to the end portion of the stud.
6. An assembly according to claim 5, in which the end stop member is received at least partly within a second - 9 recess on the axially outer side of the screw member, one or more passageways in the screw member opening into the second recess.
7. An assembly according to claim 5 or 6, in which the end stop member is immovably fixed to the stud.
8. An assembly according to any of claims 5 to 7, in which the end stop member is an end cap completely enclosing the end of the stud.
9. A hydraulic fastener assembly comprising a stud including a screw threaded end portion, a screw member screw threadingly engaging the screw threaded end portion of the stud, an end stop member on an axially outer side of the screw member and in axially fixed relationship to the end portion of the stud, and a sliding member on an axially inner side of the screw member slidably mounted on the stud and slidably engaging the screw member, the screw member including one or more passageways extending from one side of the screw member to the other to provide fluid communication between the inner and outer sides of the screw member.
10. A hydraulic fastener assembly substantially as herein described with references to and as shown by the accompanying drawings.
11. A method of operating a hydraulic fastener assembly, according to any preceding claim, the method including the steps of: introducing hydraulic fluid into the assembly to cause the sliding member to move axially inwardly away from the - 10 screw member; and subsequently screwing the screw member axially along the stud towards the sliding member.
12. A method according to claim 11, in which the screw member is screwed along the stud until it abuts the sliding member.
13. A method of operating a hydraulic fastener assembly, the method being substantially as herein described with reference to and as shown by the accompanying drawings.