Hydraulic hammer having variable stroke control

Patent metadata

Field	Value
Publication number	US-2016176033-A1
Application number	US-201414574326-A
Country	US
Kind code	A1
Filing date	Dec 17, 2014
Priority date	Dec 17, 2014
Publication date	Jun 23, 2016
Grant date	—

Abstract

A variable stroke control system for a hydraulic hammer is disclosed. The variable stroke control system may include an inlet groove formed around a piston associated with the hydraulic hammer and configured to receive pressurized fluid, and an outlet groove formed around the piston associated with the hydraulic hammer and configured to discharge the pressurized fluid. The variable stroke control system may further include a valve in fluid communication with the inlet groove and the outlet groove, and configured to selectively adjust a stroke length of the piston based on a change in pressure differential between the inlet groove and the outlet groove.

First claim

What is claimed is:

1 . A variable stroke control system for a hydraulic hammer, comprising:
an inlet groove formed around a piston associated with the hydraulic hammer and configured to receive pressurized fluid; an outlet groove formed around the piston associated with the hydraulic hammer and configured to discharge the pressurized fluid; and a valve in fluid communication with the inlet groove and the outlet groove, and configured to selectively adjust a stroke length of the piston based on a change in pressure differential between the inlet groove and the outlet groove.

2 . The variable stroke control system of claim 1 , wherein the pressure differential is indicative of a hardness of a material impacted by a work tool of the hydraulic hammer.

3 . The variable stroke control system of claim 1 , wherein the valve is configured to cause the stroke length of the piston to be longer when the pressure differential is greater than a threshold amount.

4 . The variable stroke control system of claim 3 , wherein the valve is configured to cause the stroke length of the piston to be shorter when the pressure differential is less than the threshold amount.

5 . The variable stroke control system of claim 1 , wherein the valve includes:
a valve element configured to move between a flow blocking position and a flow passing position; and a spring configured to bias the valve element to the flow blocking position.

6 . The variable stroke control system of claim 5 , wherein the valve element is moved to the flow blocking position when the pressure differential is greater than a threshold amount, and the valve element is moved to the flow passing position when the pressure differential is less than the threshold amount.

7 . The variable stroke control system of claim 1 , further including an orifice disposed between the outlet groove and a return tank, the orifice being configured to reduce a mass flow rate of fluid flowing therethrough.

8 . The variable stroke control system of claim 7 , further including a check valve disposed between the outlet groove and the orifice, the check valve being configured to provide a unidirectional flow from the outlet groove to the orifice.

9 . The variable stroke control system of claim 1 , wherein the valve is a first valve, and the variable stroke control system further includes a second valve configured to control a transition timing between upward and downward movements of the piston.

10 . The variable stroke control system of claim 9 , wherein the first valve is configured to delay a transition from an upward movement of the piston to a downward movement of the piston.

11 . The variable stroke control system of claim 1 , further including a pressure control valve configured to cause the piston to return to an uppermost position when a hammer operation has stopped, and to cause an initial stroke of the piston to be longer than a subsequent stroke of the piston

12 . A variable stroke control system for a hydraulic hammer, comprising:
an inlet groove formed around a piston associated with the hydraulic hammer and configured to receive pressurized fluid; an outlet groove formed around the piston associated with the hydraulic hammer and configured to discharge the pressurized fluid; and a valve in fluid communication with the inlet groove and the outlet groove, and configured to selectively adjust a stroke length of the piston based on a hardness of a material impacted by a work tool of the hydraulic hammer, wherein an initial stroke of the piston is longer than a subsequent stroke of the piston.

13 . The variable stroke control system of claim 12 , further including a pressure control valve configured to cause the piston to return to an uppermost position when a hammer operation has stopped, and to cause the initial stroke of the piston to be longer than the subsequent stroke of the piston.

14 . The variable stroke control system of claim 12 , wherein the valve is configured to selectively adjust the stroke length of the piston based on a change in pressure differential between the inlet groove and the outlet groove.

15 . The variable stroke control system of claim 14 , wherein the valve is configured to cause the stroke length of the piston to be longer when the pressure differential is greater than a threshold amount.

16 . The variable stroke control system of claim 15 , wherein the valve is configured to cause the stroke length of the piston to be shorter when the pressure differential is less than the threshold amount.

17 . The variable stroke control system of claim 14 , wherein the valve includes:
a valve element configured to move between a flow blocking position and a flow passing position; and a spring configured to bias the valve element to the flow blocking position.

18 . The variable stroke control system of claim 17 , wherein the valve element is moved to the flow blocking position when the pressure differential is greater than a threshold amount, and the valve element is moved to the flow passing position when the pressure differential is less than the threshold amount.

19 . The variable stroke control system of claim 14 , further including:
an orifice disposed between the outlet groove and a return tank, the orifice being configured to reduce a mass flow rate of fluid flowing therethrough; and a check valve disposed between the outlet groove and the orifice, the check valve being configured to provide a unidirectional flow from the outlet groove to the orifice.

20 . A hydraulic hammer system, comprising:
a piston; a sleeve disposed external and co-axial to the piston; an inlet groove formed at a first internal surface of the sleeve and configured to receive pressurized fluid from a pump; an outlet groove formed at a second internal surface of the sleeve and configured to direct pressurized fluid to a return tank, the outlet groove being fluidly connected to the inlet groove; a first valve configured to control a transition timing between upward and downward movements of the piston; and a second valve in fluid communication with the inlet groove and the outlet groove, and configured to selectively adjust a stroke length of the piston by delaying the transition timing of the first valve.

Assignees

• Caterpillar Inc

Inventors

• Juvonen Vaino Esko
• Moore Cody

Classifications

• B25D9/145

  for hydraulically actuated hammers having an accumulator · CPC title

• B25D9/26 Primary

  Control devices for adjusting the stroke of the piston or the force or frequency of impact thereof {(control systems adapted for earth drilling E21B44/00)} · CPC title

• B25D9/18

  involving a piston-type slide valve · CPC title