Dunlop Tyre Pressure Guages - 2 styles

Tyre pressure gauge. I have found 2 styles of markings on the gauges

The difference are:
- in the letter font for "Dunlop",
- the Dunlop symbol (D in a > ie D>) is not present on the first,
- 2 of the 3 patent numbers are missing on the second and
- coded No 6 on the first and G/6 on the second,

I have included the patent abstracts and a link to the full patent description, at the end.

1) The markings on the first are
"Dunlop,
Pressure Gauge,
No 6   6-50lbs,
Patent No, 515877, 568330, 724036
REG Des. No 829740
Made in England" on barrel

 

2)
Makers marks on the second
"Dunlop,
Pressure Gauge,
(D>) G/6   6-50lbs,
Brit Pat No, 724036
REG Des No 829740
Made in England"
on barrel

Have found the details for the patent numbers quoted on the gauges. The earliest patent was 1938, then 1943 and the most recent 1953. As both gauges have the 1953 patent both would have been made post 1953. No evidence found of which was the earlier version. Both have the same registered design number. This number was not available on line through the National Archive in England.

Abstracts from Espacenet (worldwide.espacenet.com)

1) Abstract of  Patent No 515877  (A)

                      

515,877. Helical springs. TURNER, H., and BROWN, T. July 7, 1938, No. 20094. [Class 108 (iii)] An adjustable anchorage for helical spring 12 includes a web 15 or projection adapted to engage between adjacent coils of the spring and locking means for preventing relative rotation of the spring and web which are capable of being rendered effective at will. As shown, a segmental web 15 is carried by a flanged sleeve 13 and is adapted .to be screwed into the spring 12. A flanged sleeve 18 is slotted to engage the bent end 16 of the spring. The sleeves are clamped together. The web may be helical and may be carried by a member -dispersed internally of the spring. The invention is shown applied to a tyre pressure-gauge.
For full patent description use this link  Patent Number 515877

 

Abstract of  GB568330  (A)   

568,330. Pneumatic - tyre pressure gauges. TURNER, H., and BROWN, T. June 5, 1943, No. 9030. [Class 106 (ii)] In a tyre-pressure gauge of the kind in which the air pressure moves a piston 15 in a cylinder 10 against the action of a spring 16 to protrude a graduated indicating member 20, the indicator is retained in the protruded position by friction caused by balls 23 slidable in a guide 22 in the indicator and pressed against the cylinder wall by the pressure of a spring 24 acting through a third ball 25. In a modification, the spring may be placed directly between the balls. Alternatively, one ball only may be provided, pressed radially outwards by a spring. In another form, Fig. 5, the friction is caused by a pair of segments 31 housed in a groove 30 in the indicator 20 and pressed into contact with the cylinder walls 10 by a spring 28. Specification 515,877, [Group XXXII], is referred to.

For full patent description use this link Patent Number 568330
 

Abstract of  GB724036  (A)                                                                    

                      

724,036. Pressure gauges. PNEUMATIC COMPONENTS, Ltd. Sept. 3, 1953 [Sept. 15, 1952], No. 23082/52. Class 106 (2). A soft rubber washer 14 is held in place in a coupling head of a tyre-pressure gauge by a screwed unseating pin 16 having a flange 11 that bears against a hard washer 12 housed in an internal groove in the soft rubber washer 14.
For full patent description use this link Patent Number 724036