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A polish rod clamping device, for use as part of a wellhead production pumping tree to secure a polish rod. The device includes a pressure-containing body forming a central vertical and opposed first and second side bores. A pair of clamping rams are positioned in the side bores for sliding movement

A polish rod clamping device, for use as part of a wellhead production pumping tree to secure a polish rod. The device includes a pressure-containing body forming a central vertical and opposed first and second side bores. A pair of clamping rams are positioned in the side bores for sliding movement therealong, each clamping ram having a front and a rear end, the front ends of the clamping rams being configured to accommodate at least a portion of the polish rod between their front ends when the clamping rams are advanced across the central bore. The front end of at least one of the clamping rams is configured with a vertical V-groove for gripping the polish rod. The invention extends to the V-groove rams themselves and to composite wellhead assemblies containing the V-groove clamping device.

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What is claimed is: 1. A clamping device for use as part of a wellhead to secure a tubular member, comprising: a pressure-containing body forming a central bore, which extends vertically through the body and through which the tubular member may extend, and opposed side bores extending radially outw

What is claimed is: 1. A clamping device for use as part of a wellhead to secure a tubular member, comprising: a pressure-containing body forming a central bore, which extends vertically through the body and through which the tubular member may extend, and opposed side bores extending radially outwardly in opposite directions through the body and intersecting the central bore; a pair of clamping rams positioned in the side bores for sliding movement therealong, each clamping ram having a front and a rear end, the front ends of the clamping rams being configured to accommodate at least a portion of the circumference of the tubular member between their front ends when the clamping rams are advanced across the central bore; the front end of at least one of the clamping rams being configured with a vertical V-groove for gripping the tubular member such that a portion of the circumference of the tubular member is accommodated within the V-groove at contact points in the V-groove; and an actuator connected to the rear end of each clamping ram for advancing and withdrawing the ram in the side bore, between a gripping position when the rams are advanced across the central bore into contact with the tubular member with the portion of the circumference of the tubular member accommodated within the V-groove, and a releasing position when the rams are withdrawn from the tubular member. 2. A polish rod clamping device, for use as part of a wellhead production pumping tree to secure a polish rod forming the upper end of a rod string extending through a vertical bore formed by the pumping tree, comprising: a pressure-containing body forming a central bore, which extends vertically through the body and through which the polish rod may extend, and opposed side bores extending radially outwardly in opposite directions through the body and intersecting the central bore; a pair of clamping rams positioned in the side bores for sliding movement therealong, each clamping ram having a front and a rear end, the front ends of the clamping rams being configured to accommodate at least a portion of the circumference of the polish rod between their front ends when the clamping rams are advanced across the central bore; the front end of one or both of the clamping rams being configured with a vertical V-groove for gripping the polish rod such that a portion of the circumference of the polish rod is accommodated within the V-groove at contact points in the V-groove; and an actuator connected to the rear end of each clamping ram for advancing and withdrawing the ram in the side bore, between a polish rod gripping position when the rams are advanced across the central bore into contact with the polish rod with the portion of the circumference of the polish rod accommodated within the V-groove, and a polish rod releasing position when the rams are withdrawn from the polish rod. 3. The clamping device of claim 2, wherein: to accommodate the polish rod, both of the clamping rams are configured with a vertical groove extending the entire length of the front end of the clamping ram one or more portions of the vertical groove are configured with the V-groove; one or more portions of the vertical groove are configured with an arcuate radial groove located above, below or between the one or more V-groove portions; and the clamping rams are configured to have mirror symmetry with each other. 4. The clamping device of claim 2, wherein both of the clamping rams are configured with the vertical V-groove and the V-grooves on each clamping ram aligns with each other when in the polish rod gripping position for gripping the polish rod. 5. The clamping device of claim 4, wherein the front end of each of the clamping rams carries one or more polish rod seals for sealing against the polish rod. 6. The clamping device of claim 2, wherein the front end of one or both of the clamping rams carries one or more polish rod seals for sealing against the polish rod, and wherein the one or more seals are located separately from a portion of the V-groove that grips the polish rod, such that a sealing area to the polish rod is separate from the gripping portion of the V-groove. 7. The clamping device of claim 5, wherein the clamping rams are steel bodied rams. 8. The clamping device of claim 7, wherein the one or more polish rod seals are provided by a seal which extends horizontally across the front face of the rams and across a semi-circular anti-extrusion sealing area formed adjacent the apex of the V-groove. 9. The clamping device of claim 8, wherein the semi-circular anti-extrusion sealing area is has a diameter which is equal to or greater than the diameter of the polish rod. 10. The clamping device of claim 9, wherein the semi-circular anti-extrusion sealing area is located generally centrally within the V-groove. 11. The clamping device of claim 10, wherein the seal also extends longitudinally along the sides of the ram body to seal across the central bore. 12. The clamping device of claim 7, wherein the one or more polish rod seals is provided by a thermoplastic seal insert carried at the front end of the steel bodied ram, and wherein the V-groove is formed in the steel bodied ram. 13. The clamping device of claim 2, wherein the V-groove extends vertically along the entire front end of the clamping ram. 14. The clamping device of claim 4, wherein the V-groove extends vertically along the entire front end of both of the clamping rams. 15. The clamping device of claim 7, wherein the one or more polish rod seals are located separately from a portion of the V-groove that grips the polish rod, such that a sealing area to the polish rod is separate from the gripping portion of the V-groove. 16. The clamping device of claim 8, wherein the V-groove extends vertically along the front end of each of the clamping rams above and below the seal. 17. The clamping device of claim 11, wherein the V-groove extends vertically along the entire front end of each of the clamping rams, above and below the seal. 18. The clamping device of claim 7, wherein the front ends of the clamping rams are configured such that the one or more polish rod seals contact each other in sealing relationship to seal the central bore, with the polish rod being gripped and sealed within the aligned V-grooves, when the clamping rams are in the polish rod gripping position. 19. The clamping device of claim 11, wherein the front ends of the clamping rams are configured such that the seals contact each other in sealing relationship to seal the central bore, with the polish rod being gripped within the aligned V-grooves and sealed within the semi-circular anti-extrusion sealing area, when the clamping rams are in the polish rod gripping position. 20. The clamping device of claim 19, wherein the semi-circular anti-extrusion sealing area forms an opening at its leading edge which is equal to or larger than the diameter of the polish rod. 21. The clamping device of claim 19, wherein the V-groove forms an opening at its leading edge which is larger than the diameter of the polish rod. 22. The clamping device of claim 19, wherein the V-groove and the semi-circular anti-extrusion sealing area form openings at their leading edges, and wherein the leading edge of the V-groove is rearwardly recessed relative to the leading edge of the semi-circular anti-extrusion sealing area. 23. The clamping device of claim 2, wherein the V-groove is hardened, textured, coated or modified to carry an insert which may be hardened, textured, or coated, in order to enhance frictional contact or grip to the polish rod. 24. The clamping device of claim 19, wherein the V-groove is hardened, textured, coated or modified to carry an insert which may be hardened, textured, or coated, in order to enhance frictional contact or grip to the polish rod. 25. The clamping device of claim 2, wherein the clamping rams and side bores are generally cylindrical, and wherein the rams carry one or more seals at their rear ends for sealing against the side bores. 26. The clamping device of claim 19, wherein the clamping rams and side bores are generally cylindrical, and wherein the rams carry one or more seals at their rear ends for sealing against the side bores. 27. The clamping device of claim 2, wherein the body provides a top connector and a bottom connector for connecting and sealing to wellhead components located above and below the body. 28. The clamping device of claim 26, wherein the body provides a top connector and a bottom connector for connecting and sealing to wellhead components located above and below the body. 29. A composite wellhead assembly including, between a top connector and a bottom connector, a clamping device together with one or more of the following wellhead components, in any sequence: adapter, valve, gate valve, flow tee, and blowout preventer, said clamping device comprising: a pressure-containing body forming a central bore, which extends vertically through the body and through which the polish rod may extend, and opposed side bores extending radially outwardly in opposite directions through the body and intersecting the central bore; a pair of clamping rams positioned in the side bores for sliding movement therealong, each clamping ram having a front and a rear end, the front ends of the clamping rams being configured to accommodate at least a portion of the circumference of the polish rod between their front ends when the clamping rams are advanced across the central bore; the front end of one or both of the clamping rams being configured with a vertical V-groove for gripping the polish rod such that a portion of the circumference of the polish rod is accommodated within the V-groove at contact points in the V-groove; and an actuator connected to the rear end of each clamping ram for advancing and withdrawing the ram in the side bore, between a polish rod gripping position when the rams are advanced across the central bore into contact with the polish rod with the portion of the circumference of the polish rod accommodated within the V-groove, and a polish rod releasing position when the rams are withdrawn from the polish rod. 30. The clamping device of claim 28, further comprising the clamping device together with one or more of the following wellhead components, in any sequence: adapter, valve, gate valve, flow tee, and blowout preventer located between the top connector and the bottom connector. 31. A clamping ram, for use as part of a wellhead production pumping tree to secure a polish rod forming the upper end of a rod string extending through a vertical bore formed by the pumping tree, the pumping tree providing a pressure-containing body forming a central bore, which extends vertically through the body and through which the polish rod may extend, and opposed side bores extending radially outwardly in opposite directions through the body and intersecting the central bore, the clamping ram comprising; a clamping ram adapted to be positioned in one of the side bores for sliding movement therealong, the clamping ram having a front and a rear end, the front end being configured to accommodate, with an opposing clamping ram, at least a portion of the circumference of the polish rod when the clamping ram and the opposing clamping ram are advanced across the central bore, and the front end being configured with a vertical V-groove for gripping the polish rod such that a portion of the circumference of the polish rod is accommodated within the V-groove at contact points in the V-groove. 32. The clamping ram of claim 31, wherein: the clamping ram is a steel bodied ram; the front end of the clamping ram is configured to contact and seal to an opposing mirror image clamping ram; the front end of the clamping ram carries one or more polish rod seals extending horizontally across the front face of the ram and across a semi-circular anti-extrusion sealing area located generally centrally within the V-groove, the semi-circular anti-extrusion sealing area being formed adjacent the apex of the V-groove and having a diameter which is equal to or greater than the diameter of the polish rod: the clamping ram further includes seals extending longitudinally along the sides of the ram body to seal across the central bore. 33. The clamping ram of claim 32, wherein the V-groove is hardened, textured, coated or modified to carry an insert which may be hardened, textured, or coated, in order to enhance frictional contact or grip to the polish rod. 34. The clamping ram of claim 33, wherein the clamping ram is generally cylindrical, and carries one or more seals at the rear end for sealing against the side bores.